Moved material editing from component window to asset editor

- EditorContentManager now returns null if asset wasn't found (instead of crashing)
- FixUp asset identifier when dragging from asset browser
- Lock current asset in properties editor

GlitchyEngine/src/Content/Asset.bf

@@ -3,6 +3,7 @@ using System;
 using Bon;
 using Bon.Integrated;
 using System.Reflection;
+using System.IO;
 
 namespace GlitchyEngine.Content;