Forbid pasting content below a shortcut, to prevent loops on purge and other operations. Fixes bug #11855.

lib/WebGUI/Asset/Shortcut.pm

@@ -789,6 +789,19 @@ sub notLinked {
 
 #-------------------------------------------------------------------
 
+=head2 paste ( )
+
+Pasting assets under a Shortcut can cause lots of problems, including infinite loops
+for operations like paste, and purge.
+
+=cut
+
+sub paste {
+    return 0;
+}
+
+#-------------------------------------------------------------------
+
 =head2 prepareView ( )
 
 See WebGUI::Asset::prepareView() for details.  Extends the base class to call prepareView