ext4: ignore last group w/o enough space when resizing instead of BUG'ing

If the last group does not have enough space for group tables, ignore
it instead of calling BUG_ON().

Reported-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org