linux: theme handling bugfix (#3515)

* linux: theme handling bugfix

* update changelog

Author: tmclane

mkdocs-website/docs/en/changelog.md

@@ -37,6 +37,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- [linux] Fixed theme handling error on NixOS by [tmclane](https://github.com/tmclane) in [#3515)(https://github.com/wailsapp/wails/pull/3515)
 - Fixed cross volume project install for windows by [atterpac](https://github.com/atterac) in [#3512](https://github.com/wailsapp/wails/pull/3512)
 - Fixed react template css to show footer by [atterpac](https://github.com/atterpac) in [#3477](https://github.com/wailsapp/wails/pull/3477)
 - Fixed zombie processes when working in devmode by updating to latest refresh by [Atterpac](https://github.com/atterpac) in [#3320](https://github.com/wailsapp/wails/pull/3320).

v3/pkg/application/application_linux.go

@@ -156,10 +156,10 @@ func (a *linuxApp) monitorThemeChanges() {
 			if len(body) < 2 {
 				return "", false
 			}
-			if body[0].(string) != "org.gnome.desktop.interface" {
+			if entry, ok := body[0].(string); !ok || entry != "org.gnome.desktop.interface" {
 				return "", false
 			}
-			if body[1].(string) == "color-scheme" {
+			if entry, ok := body[1].(string); ok && entry == "color-scheme" {
 				return body[2].(dbus.Variant).Value().(string), true
 			}
 			return "", false