url may cause nginx work process crash
the code in src/http/ngx_http_request.c:ngx_http_free_request
[b]r->upstream may be a NULL pointer[/b]


#0 0x000000000042b368 in ngx_http_free_request (r=0x13b60c20, rc=0) at src/http/ngx_http_request.c:2951
2951 switch (r->upstream->cache_status) {
(gdb) bt
#0 0x000000000042b368 in ngx_http_free_request (r=0x13b60c20, rc=0) at src/http/ngx_http_request.c:2951
#1 0x000000000042b5d1 in ngx_http_close_request (r=<value optimized out>, rc=0) at src/http/ngx_http_request.c:2910
#2 0x000000000042de75 in ngx_http_finalize_connection (r=0x13b60c20) at src/http/ngx_http_request.c:2145
#3 0x000000000042e4a1 in ngx_http_finalize_request (r=<value optimized out>, rc=<value optimized out>)
at src/http/ngx_http_request.c:2045
#4 0x000000000042e12c in ngx_http_finalize_request (r=0x13b60c20, rc=400) at src/http/ngx_http_request.c:1929
#5 0x000000000042f97e in ngx_http_process_request_line (rev=0x13b740a8) at src/http/ngx_http_request.c:900
#6 0x0000000000421583 in ngx_epoll_process_events (cycle=0x13b56b90, timer=<value optimized out>, flags=<value optimized out>)
at src/event/modules/ngx_epoll_module.c:642
#7 0x0000000000419038 in ngx_process_events_and_timers (cycle=0x13b56b90) at src/event/ngx_event.c:261
#8 0x000000000041ef50 in ngx_single_process_cycle (cycle=0x13b56b90) at src/os/unix/ngx_process_cycle.c:306
#9 0x000000000040473b in main (argc=16, argv=0x13b560a0) at src/core/nginx.c:393