mms: Fix NPE when attaching slides

Issue: BACON-908

Change-Id: I7cc2fa975852cb08612849266529ee8aaf25b071
mms: do not close database

JIRA: BUGDUMP-22916
https://jira.cyanogenmod.org/browse/BUGDUMP-22916
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>

Change-Id: I1ce4d8e3d8b1bb482e5556e20e9bb76dbf522abf