Bug 1061970: Check if JS variable 'this._statements' is defined before using it (and use 'for...of'), in CPS2_destroy(). r=adw

toolkit/components/contentprefs/ContentPrefService2.jsm

@@ -654,8 +654,10 @@ ContentPrefService2.prototype = {
   },
 
   destroy: function CPS2_destroy() {
-    for each (let stmt in this._statements) {
-      stmt.finalize();
+    if (this._statements) {
+      for (let stmt of this._statements) {
+        stmt.finalize();
+      }
     }
   },