FIX: add return value to onGeolocationRequest actor command handler to prevents muted remote debugger actor problem

apparently every actor handler needs to return a value to fully prevents
the muted debugger actor/connection problem:

https://bugzilla.mozilla.org/show_bug.cgi?id=855509
Merge pull request #401 from rpl/fix-muted-remote-debugger-actor

FIX: add return value to onGeolocationRequest actor command handler to prevents muted remote debugger actor problem