panic: kernel diagnostic assertion "oip->i_size == 0" failed in file
    "/src/sys/ufs/ffs/ffs_inode.c", line 231
cpu0: Begin traceback...
?(?)
db_panic at 0
vpanic + 188
kern_assset + 14
ffs_truncate + 7c
ufs_truncate_all + 62
ufs_inactive + 38
VOP_INACTIVE + 26
vrelel(?)
genfs_ufslike_remove_check_permitted + 4be
vput + ac
ufs_remove + aa
VOP_REMOVE + fa
do_sys_unlink (?)
VOP_MKDIR + 144
sys_unlink + 16
syscall_plain + c4
syscall + 5c
trap0 + e
cpu0: End traceback...