Check if mText is null before invoke toString()

Change-Id: I8b519fa42e928eb157248e6b896a8958f281f9cd
Signed-off-by: Roger Chen <cxr514033970@gmail.com>
Remove DEBUG to avoid to run checking at every turn

Needn't to run storage checking in DEBUG mode at every turn,
it will make "DELETE OLD MSGS" always be checked in Mms Settings

Change-Id: I4412f6771695c84371cee543ec2276285f3fca07
Signed-off-by: Roger Chen <cxr514033970@gmail.com>