Fix the crash when applying daily wallpaper without network connection

It's because CustomizationPickerActivity is cast to BaseActivity to call isSafeToCommitFragmentTransaction(), but it is not a BaseActivity.
Extract isSafeToCommitFragmentTransaction() to an interface to let CustomizationPickerActivity to implement it.

Bug: 167943713
Change-Id: Idd392fbd2fbadf3d8f4d69fb68ba1ccec948306a
1 file changed