ext4: fix uninitialized variable in ext4_inlinedir_to_tree

ext4: fix uninitialized variable in ext4_inlinedir_to_tree

Syzbot has found an uninit-value bug in ext4_inlinedir_to_tree

This error happens because ext4_inlinedir_to_tree does not
handle the case when ext4fs_dirhash returns an error

This can be avoided by checking the return value of ext4fs_dirhash
and propagating the error,
similar to how it's done with ext4_htree_store_dirent

Signed-off-by: Xiaxi Shen <shenxiaxi26@gmail.com>
Reported-and-tested-by: syzbot+eaba5abe296837a640c0@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=eaba5abe296837a640c0
Link: https://patch.msgid.link/20240501033017.220000-1-shenxiaxi26@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>