Handle null cursor

If for some reason the SmsProvider returns a null cursor when we try
and load the SIM messages, show the "no sim messages" UI rather than
leaving the UI in a constant loading (animated loading cursor) state.
This is part three of three fixes for BC-triaged bug 2205782.

Change-Id: Ie3dceea621f8c2aa0a2c98f79278c120df3c37e7
1 file changed