Gallery2: Make sure no NPE happens

Author: Michael W <baddaemon87@gmail.com>
Date:   Sat Jun 4 16:10:05 2016 +0200

    Gallery2: Make sure no NPE happens

    Fix for the case when getExternalCacheDir returns null

    Change-Id: I15f4a4a37ac44d70d14ac08cd743d3327f91dde1

Author: Michael W <baddaemon87@gmail.com>
Date:   Tue Jun 7 21:05:00 2016 +0200

    Gallery2: Remove more possible NPEs

    getCache can return null ->
    check this before proceeding

    Change-Id: I834780a4dafbe22f2d345fe5571cb20f3f3e5e2e

Change-Id: I820d8314f855329885f6b7ca710efa981b9d327c