ext4: avoid trying to kfree an ERR_PTR pointer

Thanks to Dan Carpenter for extending smatch to find bugs like this.
(This was found using a development version of smatch.)

Fixes: 36de928641ee48b2078d3fe9514242aaa2f92013
Reported-by: Dan Carpenter <dan.carpenter@oracle.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
2 files changed