Bug 1206491 - Fix a JavaScript error in about:cache page. r=mayhemmer

toolkit/components/aboutcache/content/aboutCache.js

@@ -10,7 +10,8 @@ var storage = searchParams.get('storage');
 var context = searchParams.get('context');
 
 // The context is in a format as used by the HTTP cache v2 back end
-var [context, isAnon, isInBrowser, appId, isPrivate] = context.match(/(a,)?(b,)?(i\d+,)?(p,)?/);
+if (context)
+  var [context, isAnon, isInBrowser, appId, isPrivate] = context.match(/(a,)?(b,)?(i\d+,)?(p,)?/);
 if (appId)
   appId = appId.match(/i(\d+),/)[1];