btrfs: send: handle path ref underflow in header iterate_inode_ref()

mainline inclusion
from mainline-v6.9-rc1
commit 3c6ee34c6f9cd12802326da26631232a61743501
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9QGIK
CVE: CVE-2024-35935

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3c6ee34c6f9cd12802326da26631232a61743501



--------------------------------

Change BUG_ON to proper error handling if building the path buffer
fails. The pointers are not printed so we don't accidentally leak kernel
addresses.

Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Wang Zhaolong <wangzhaolong1@huawei.com>