ui.gadgets.worlds: rethrow error so traceback is more obvious.

basis/ui/gadgets/worlds/worlds.factor

@@ -219,7 +219,7 @@ ui-error-hook [ [ rethrow ] ] initialize
             dup [ draw-world* ] with-gl-context
             flush-layout-cache-hook get call( -- )
         ] [
-            swap f >>active? <world-error> throw
+            swap f >>active? <world-error> rethrow
         ] recover
     ] [ drop ] if ;