Bug 1327953 - Fix enabling the 'Restore Default Search Engines' button when removing a default engine, r=Standard8.

browser/components/preferences/in-content/search.js

@@ -397,9 +397,9 @@ EngineStore.prototype = {
     if (index == -1)
       throw new Error("invalid engine?");
 
-    this._engines.splice(index, 1);
+    let removedEngine = this._engines.splice(index, 1)[0];
 
-    if (this._defaultEngines.some(this._isSameEngine, this._engines[index]))
+    if (this._defaultEngines.some(this._isSameEngine, removedEngine))
       gSearchPane.showRestoreDefaults(true);
     gSearchPane.buildDefaultEngineDropDown();
     return index;