src/Tools/jEdit/src/jedit/TheoryView.scala

     val document = current_document()
     val offset = from_current(document, text_area.xyToOffset(x, y))
     document.command_at(offset) match {
       case Some(cmd) =>
         document.token_start(cmd.tokens.first)
-        cmd.type_at(document, offset - cmd.start(document))
+        cmd.type_at(document, offset - cmd.start(document)).getOrElse(null)
       case None => null
     }
   }