skip filter class checker (#207)

* skip filter class checker

* format patch

---------

Co-authored-by: Eric Tucker <[email protected]>

Author: khaledhatahet

src/Filterable.php

@@ -21,19 +21,23 @@ trait Filterable
      */
     public function scopeFilter($query, array $input = [], $filter = null)
     {
-        // Resolve the current Model's filter
         if ($filter === null) {
-            $filter = $this->getModelFilterClass();
+            if (class_exists($this->getModelFilterClass())) {
+                $filter = $this->getModelFilterClass();
+
+                $modelFilter = new $filter($query, $input);
+
+                // Set the input that was used in the filter (this will exclude empty strings)
+                $this->filtered = $modelFilter->input();
+
+                // Return the filter query
+                return $modelFilter->handle();
+            }
         }
 
         // Create the model filter instance
-        $modelFilter = new $filter($query, $input);
-
-        // Set the input that was used in the filter (this will exclude empty strings)
-        $this->filtered = $modelFilter->input();
 
-        // Return the filter query
-        return $modelFilter->handle();
+        return $query;
     }
 
     /**