panic: vm_object_reference_locked: dead object referenced

On 7.0:

db> wh
Tracing pid 666 tid 100041 td 0xc325d1b0
kdb_enter(c0640fe0) at kdb_enter+0x2b
panic(c0657511,c9f85934,e38a9bac,c05cf2e8,c9f85934) at panic+0xbb
vm_object_reference_locked(c9f85934,386,0,0,0) at vm_object_reference_locked+0x2c
vm_object_split(c0c42c38,c4bc0770,c0c42c38,c2fd1318,e38a9bf0) at vm_object_split+0xf8
vm_map_copy_entry(c2fd1318,c56a9528,c0c42c38,c4bc0770) at vm_map_copy_entry+0x97
vmspace_fork(c2fd1318,c4bce120,c4bcf234,c37b2a00,e38a9c64) at vmspace_fork+0x1f8
vm_forkproc(c325d1b0,c4bcf234,c48adbd0,14,c4bcf29c,0,c063e175,298,c069a760,c063e175,294) at vm_forkproc+0xb3
fork1(c325d1b0,14,0,e38a9c7c,e38a9cac) at fork1+0xe15
fork(c325d1b0,e38a9d04,7,c,c325d1b0) at fork+0x18
syscall(3b,3b,bfbf003b,1,1) at syscall+0x27e
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (2, FreeBSD ELF32, fork), eip = 0x28318963, esp = 0xbfbfdeec, ebp = 0xbfbfee98 ---

Core available.

Kris