Fix to NullPointerException when activity is relaunched

When ChooseTypeAndAccountActivity is relaunched and resumed
by ActivityManager a call is made to onActivityResult without
first triggering onResume. This leads to mAccounts object
still being null.

Fixed by properly setting mAccounts object if it is null prior
to use after function onCreate has been called.

Change-Id: Ife7e1e052c473970d923fa43ee6189eb62a1113b