Panic in fellow_cache_obj_iter()

Originally reported by @d.rad in #7 (comment 1329659634)

Child (13193) Panic at: Mon, 27 Mar 2023 14:32:46 GMT 
Wrong turn at cache/cache_main.c:327:
 Signal 6 (Aborted) received at 0x3de00003389 si_code -6 
version = varnish-7.3.0 
revision 84d79120b6d17b11819a663a93160743f293e63f, vrt api = 17.0
ident = Linux,4.18.0-425.13.1.el8_7.x86_64,x86_64,-junix,-sfellow,-sdefault,-Elibvmod_slash.so,-hcritbit,epoll
now = 5388.192805 (mono), 1679927559.279182 (real) 
Backtrace: 
0x56047ece660c: /usr/sbin/varnishd(+0x5b60c) \[0x56047ece660c\] 
0x56047ed6410b: /usr/sbin/varnishd(VAS_Fail+0x1b) \[0x56047ed6410b\] 
0x56047ece10ea: /usr/sbin/varnishd(+0x560ea) \[0x56047ece10ea\] 
0x7f9104547cf0: /lib64/libpthread.so.0(+0x12cf0) \[0x7f9104547cf0\] 
0x7f91041bdaff: /lib64/libc.so.6(gsignal+0x10f) \[0x7f91041bdaff\] 
0x7f9104190ea5: /lib64/libc.so.6(abort+0x127) \[0x7f9104190ea5\] 
0x7f9104190d79: /lib64/libc.so.6(+0x21d79) \[0x7f9104190d79\] 
0x7f91041b6456: /lib64/libc.so.6(+0x47456) \[0x7f91041b6456\] 
0x7f91014bcf5d: vext_cache/libvmod_slash.so,iadatcdb.so(+0x10f5d) \[0x7f91014bcf5d\] 
0x7f91014fa95c: vext_cache/libvmod_slash.so,iadatcdb.so(fellow_cache_obj_iter+0x85c) \[0x7f91014fa95c\] 
errno = 104 (Connection reset by peer) 
argv = {
 \[0\] = "/usr/sbin/varnishd",
 \[1\] = "-E",
 \[2\] = "/usr/lib64/varnish/vmods/libvmod_slash.so",
 \[3\] = "-P",
 \[4\] = "/var/run/varnish.pid",
 \[5\] = "-f",
 \[6\] = "/etc/varnish/default.vcl",
 \[7\] = "-a",
 \[8\] = ":80",
 \[9\] = "-T",
 \[10\] = "127.0.0.1:6082",
 \[11\] = "-t",
 \[12\] = "120",
 \[13\] = "-S",
 \[14\] = "/etc/varnish/secret",
 \[15\] = "-s",
 \[16\] = "fast=fellow,/var/lib/varnish/varnish_storage.bin,40G,16G,2MB",
 \[17\] = "-p",
 \[18\] = "thread_pool_min=5",
 \[19\] = "-p",
 \[20\] = "thread_pool_max=2500",
 \[21\] = "-p",
 \[22\] = "thread_pool_timeout=300",
 \[23\] = "-p",
 \[24\] = "thread_pools=4", }