Fix exception in Custom Editors UI due to invalid reference value processing

#325

Source/Editor/CustomEditors/Values/ValueContainer.cs

@@ -251,6 +251,10 @@ namespace FlaxEditor.CustomEditors
             }
             if (instanceValues._hasReferenceValue)
             {
+                // If the reference value is set for the parent values but it's null object then skip it
+                if (instanceValues._referenceValue == null && !instanceValues.Type.IsValueType)
+                    return;
+
                 _referenceValue = Info.GetValue(instanceValues._referenceValue);
                 _hasReferenceValue = true;
             }

Source/Engine/UI/GUI/Control.cs

@@ -209,7 +209,6 @@ namespace FlaxEngine.GUI
         public bool Enabled
         {
             get => _isEnabled;
-
             set
             {
                 if (_isEnabled != value)
@@ -255,7 +254,6 @@ namespace FlaxEngine.GUI
         public bool Visible
         {
             get => _isVisible;
-
             set
             {
                 if (_isVisible != value)