Profile editor - Fix undoing profile editor commands

- Undoing a change to an existing keyframe's value restores the value instead of deleting the keyframe
- Undoing "remove effect" puts the effect back in its place instead of below the next one
- Undoing "toggle keyframes" restores what it was before
- Undoing a brush change on a layer that had no brush removes the brush again, using the new Layer.RemoveLayerBrush
- Undoing "add element" disables the element again
- Undoing an event path change back to no path goes back to an event start node, like a new condition
- MoveProfileElement says "Move folder" for folders
- UpdateLayerProperty without a time no longer calls itself "Add ... keyframe"

src/Artemis.Core/Models/Profile/Conditions/EventCondition.cs

@@ -167,15 +167,13 @@ public class EventCondition : CorePropertyChanged, INodeScriptCondition
     /// </summary>
     public void UpdateEventNode(bool updateScript)
     {
-        if (EventPath == null)
+        Type? pathType = EventPath?.GetPropertyType();
+        if (EventPath != null && pathType == null)
             return;
 
-        Type? pathType = EventPath.GetPropertyType();
-        if (pathType == null)
-            return;
-
-        // Create an event node if the path type is a data model event
-        if (pathType.IsAssignableTo(typeof(IDataModelEvent)))
+        // Create an event node if the path type is a data model event, without a path go back to the event node a new
+        // condition starts with
+        if (pathType == null || pathType.IsAssignableTo(typeof(IDataModelEvent)))
         {
             EventConditionEventStartNode eventNode;
             // Ensure the start node is an event node

src/Artemis.Core/Models/Profile/Layer.cs

@@ -847,6 +847,24 @@ public sealed class Layer : RenderProfileElement
         ActivateLayerBrush();
     }
 
+    /// <summary>
+    ///     Removes the current layer brush, leaving the layer without a brush
+    /// </summary>
+    public void RemoveLayerBrush()
+    {
+        if (LayerBrush == null)
+            return;
+
+        BaseLayerBrush oldLayerBrush = LayerBrush;
+        General.BrushReference.SetCurrentValue(null!);
+        LayerBrush = null;
+
+        // Don't dispose the brush, only disable it
+        // That way an undo-action does not need to worry about disposed brushes
+        oldLayerBrush.InternalDisable();
+        ActivateLayerBrush();
+    }
+
     private void ActivateLayerBrush()
     {
         try