email: prevent NPE caused by null cursors

Change-Id: If819f14d4cf25d6ba35110a7a22125909a6f87dc
JIRA: CYAN-4577
Issue: https://jira.cyanogenmod.org/browse/CYAN-4577
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_packages_apps_UnifiedEmail into sokp-kk