fix: Warn when sending empty gumps (#2563)

### Summary

Generates a console warning when users receive an empty gump. This will help prevent client side leaks.

Projects/UOContent/Gumps/Base/DynamicGump.cs

@@ -47,6 +47,7 @@ public abstract class DynamicGump : BaseGump
         BuildLayout(ref gumpBuilder);
         gumpBuilder.FinalizeLayout();
 
+        HasVisualElements = gumpBuilder.HasVisualElements;
         _switches = gumpBuilder.Switches;
         _textEntries = gumpBuilder.TextEntries;