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: 36de928641
Reported-by: Dan Carpenter <dan.carpenter@oracle.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

fs/ext4/resize.c

@@ -575,6 +575,7 @@ handle_bb:
 		bh = bclean(handle, sb, block);
 		if (IS_ERR(bh)) {
 			err = PTR_ERR(bh);
+			bh = NULL;
 			goto out;
 		}
 		overhead = ext4_group_overhead_blocks(sb, group);
@@ -603,6 +604,7 @@ handle_ib:
 		bh = bclean(handle, sb, block);
 		if (IS_ERR(bh)) {
 			err = PTR_ERR(bh);
+			bh = NULL;
 			goto out;
 		}