ext4: fix potential memory leak in ext4_fc_record_modified_inode()

ext4: fix potential memory leak in ext4_fc_record_modified_inode()

As krealloc may return NULL, in this case 'state->fc_modified_inodes'
may not be freed by krealloc, but 'state->fc_modified_inodes' already
set NULL. Then will lead to 'state->fc_modified_inodes' memory leak.

Cc: stable@kernel.org
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220921064040.3693255-2-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>