Fix for default sort key crash

The existing default sort key was being cached when the dialog was
constructed, but on the 2nd time launching it the reference was broken.
This change gets rid of the caching and always grabs a fresh copy when
we need one.

Also, the flag indicating the default sort key has changed wasn't being
reset properly.

Change-Id: I8fb3b088f25212b8c542df65bb5a248550ff6f27
Merge "Fix for default sort key crash"