Fix bug with removing a removed texture reference

Vocaluxe/Lib/Draw/CDrawBase.cs

@@ -882,6 +882,8 @@ namespace Vocaluxe.Lib.Draw
         {
             if (textureRef == null)
                 return;
+            if (textureRef.ID > 0)
+            {
                 if (_MainThreadID != Thread.CurrentThread.ManagedThreadId)
                 {
                     lock (_TextureQueue)
@@ -901,6 +903,7 @@ namespace Vocaluxe.Lib.Draw
                     }
                     textureRef.SetRemoved();
                 }
+            }
             textureRef = null;
         }