mozilla-b2g/marionette-apps — pull request #41 by KevinGrandon (2014-11-12 11:06:14+00:00)
Title: Bug 1097591 - Do not explode if the home screen frame has not been constructed yet

This is kind of a guess, but I think this could possibly help?

https://bugzilla.mozilla.org/show_bug.cgi?id=1097591