Coredump info:
(gdb) bt
#0 0x0000000000004296 in ?? ()
#1 0x00007fc6d7bb898d in mod_proxy_trigger (srv=0x58a0d0, p_d=Variable "p_d" is not available.
) at mod_proxy_core.c:3140
#2 0x0000000000428a55 in plugins_call_handle_trigger (srv=0x58a0d0) at plugin.c:430
#3 0x00000000004156af in main (argc=Variable "argc" is not available.
) at server.c:636
It Can not be reproduced.
The lighttpd's version is lighttpd-1.5.0.1600