Check if mImapStore is null before attempting to open folder.

If the the port number for the carrier config is null or not a number,
mImapStore will not be initialized. This means that attempting to open
the ImapFolder will result in a NPE. Make a check first.

Bug: 21693619
Change-Id: Id1400ea41f916e26fed05db5e8343505f774e455
1 file changed