mms: fix crash when deselecting all conversations

- deselecting all conversations exits action mode, so we don't want to call invalidate

Change-Id: I9cf18748cee7b043b158246a1207994b38ac061b
Merge branch 'cm-12.0' of https://github.com/CyanogenMod/android_packages_apps_Mms-caf into cm-12.0