Fix a wrong reference.

common/content/autocommands.js

@@ -31,12 +31,14 @@ const AutoCommands = Module("autocommands", {
      * @param {string} cmd The Ex command to run.
      */
     add: function (events, regex, cmd) {
+        let self = this;
+
         if (typeof events == "string") {
             events = events.split(",");
             liberator.log("DEPRECATED: the events list arg to autocommands.add() should be an array of event names");
         }
         events.forEach(function (event) {
-            this._store.push(new AutoCommand(event, RegExp(regex), cmd));
+            self._store.push(new AutoCommand(event, RegExp(regex), cmd));
         });
     },