fix #1847 tab doesn't work for invalid css when emmet is enabled

lib/ace/ext/emmet.js

@@ -368,6 +368,7 @@ exports.runEmmetCommand = function(editor) {
     } catch(e) {
         editor._signal("changeStatus", typeof e == "string" ? e : e.message);
         console.log(e);
+        result = false
     }
     return result;
 };