Despawning an entity that has a relationship pair causes a crash on Relationship::on_replace

[hukasu]

Bevy version

0.16

What you did

#[derive(Component)]
#[relationship(relationship_target = AT)]
struct A(Entity);

#[derive(Component)]
#[relationship_target(relationship = A, linked_spawn)]
struct AT(Vec<Entity>);

#[derive(Component)]
#[relationship(relationship_target = BT)]
struct B(Entity);

#[derive(Component)]
#[relationship_target(relationship = B)]
struct BT(Vec<Entity>);

#[test]
fn remove_entity_with_multiple_relationships() {
    let mut world = World::new();

    let a = world.spawn_empty().id();
    let b = world.spawn_empty().id();

    world.entity_mut(a).insert(B(b));
    assert_eq!(world.entity(b).get::<BT>().unwrap().0[0], a);

    world.entity_mut(b).insert(A(a));
    assert_eq!(world.entity(a).get::<AT>().unwrap().0[0], b);

    world.despawn(a);
}

What went wrong

Crash report

thread 'remove_entity_with_multiple_relationships' panicked at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/error/handler.rs:141:1:
Encountered an error in command `<<relationship::B as bevy_ecs::relationship::Relationship>::on_replace::{{closure}} as bevy_ecs::error::command_handling::CommandWithEntity<core::result::Result<(), bevy_ecs::world::error::EntityMutableFetchError>>>::with_entity::{{closure}}`: The entity with ID 1v1 does not exist (enable `track_location` feature for more details)
   1: <T as core::convert::Into<U>>::into
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/core/src/convert/mod.rs:767:9
   2: <C as bevy_ecs::error::command_handling::HandleError<core::result::Result<T,E>>>::handle_error_with::{{closure}}
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/error/command_handling.rs:37:17
   3: <F as bevy_ecs::system::commands::command::Command<Out>>::apply
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/system/commands/command.rs:62:9
   4: bevy_ecs::world::command_queue::RawCommandQueue::push::{{closure}}
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/command_queue.rs:173:25
   5: core::ops::function::FnOnce::call_once
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
   6: bevy_ecs::world::command_queue::RawCommandQueue::apply_or_drop_queued::{{closure}}
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/command_queue.rs:263:26
   7: <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/core/src/panic/unwind_safe.rs:272:9
   8: std::panicking::try::do_call
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/std/src/panicking.rs:589:40
   9: std::panicking::try
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/std/src/panicking.rs:552:19
  10: std::panic::catch_unwind
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/std/src/panic.rs:359:14
  11: bevy_ecs::world::command_queue::RawCommandQueue::apply_or_drop_queued
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/command_queue.rs:268:30
  12: bevy_ecs::world::World::flush_commands
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/mod.rs:2934:17
  13: bevy_ecs::world::World::flush
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/mod.rs:2957:9
  14: bevy_ecs::world::entity_ref::EntityWorldMut::despawn_with_caller
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/entity_ref.rs:2609:15
  15: bevy_ecs::world::World::despawn_with_caller
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/mod.rs:1424:9
  16: bevy_ecs::world::World::despawn
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/mod.rs:1393:29
  17: relationship::remove_entity_with_multiple_relationships
             at ./tests/relationship.rs:32:5
  18: relationship::remove_entity_with_multiple_relationships::{{closure}}
             at ./tests/relationship.rs:20:47
  19: core::ops::function::FnOnce::call_once
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
  20: core::ops::function::FnOnce::call_once
             at /rustc/4d051fb306e661654d088892e02e69b8c0c39d43/library/core/src/ops/function.rs:250:5
note: Some "noisy" backtrace lines have been filtered out. Run with `BEVY_BACKTRACE=full` for a verbose backtrace.

stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/4d051fb306e661654d088892e02e69b8c0c39d43/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/4d051fb306e661654d088892e02e69b8c0c39d43/library/core/src/panicking.rs:75:14
   2: bevy_ecs::error::handler::panic
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/error/handler.rs:129:9
   3: bevy_ecs::error::handler::panic{{reify.shim}}
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/error/handler.rs:141:1
   4: <C as bevy_ecs::error::command_handling::HandleError<core::result::Result<T,E>>>::handle_error_with::{{closure}}
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/error/command_handling.rs:36:25
   5: <F as bevy_ecs::system::commands::command::Command<Out>>::apply
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/system/commands/command.rs:62:9
   6: bevy_ecs::world::command_queue::RawCommandQueue::push::{{closure}}
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/command_queue.rs:173:25
   7: core::ops::function::FnOnce::call_once
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
   8: bevy_ecs::world::command_queue::RawCommandQueue::apply_or_drop_queued::{{closure}}
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/command_queue.rs:263:26
   9: <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/core/src/panic/unwind_safe.rs:272:9
  10: std::panicking::try::do_call
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/std/src/panicking.rs:589:40
  11: std::panicking::try
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/std/src/panicking.rs:552:19
  12: std::panic::catch_unwind
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/std/src/panic.rs:359:14
  13: bevy_ecs::world::command_queue::RawCommandQueue::apply_or_drop_queued
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/command_queue.rs:268:30
  14: bevy_ecs::world::World::flush_commands
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/mod.rs:2934:17
  15: bevy_ecs::world::World::flush
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/mod.rs:2957:9
  16: bevy_ecs::world::entity_ref::EntityWorldMut::despawn_with_caller
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/entity_ref.rs:2609:15
  17: bevy_ecs::world::World::despawn_with_caller
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/mod.rs:1424:9
  18: bevy_ecs::world::World::despawn
             at /home/hukasu/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bevy_ecs-0.16.0/src/world/mod.rs:1393:29
  19: relationship::remove_entity_with_multiple_relationships
             at ./tests/relationship.rs:32:5
  20: relationship::remove_entity_with_multiple_relationships::{{closure}}
             at ./tests/relationship.rs:20:47
  21: core::ops::function::FnOnce::call_once
             at /nix/store/x1nk497xq60bxmbfsi6baspb7mdawbna-rust-default-1.89.0-nightly-2025-05-19/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
  22: core::ops::function::FnOnce::call_once
             at /rustc/4d051fb306e661654d088892e02e69b8c0c39d43/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.