fix: null check

Author: Bruno Mikoski

Scripts/Editor/Generators/CollectionGenerators.cs

@@ -268,7 +268,8 @@ private static void CopyFieldToSerializedProperty(
                 return;
 
             // Get the property to copy the value to.
-            serializedObject.TryFindProperty(field.Name, out SerializedProperty serializedProperty);
+            if(!serializedObject.TryFindProperty(field.Name, out SerializedProperty serializedProperty))
+                return;
 
             object value = field.GetValue(owner);