settings: check if ime switcher pref was remove previously

This could happend in tablet devices

JIRA: BUGDUMP-20712
https://jira.cyanogenmod.org/browse/BUGDUMP-20712
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>

Change-Id: I85c1d6e56f85e3220311aabc68d6532d6ffdf59f