Fixed loss of chain links in fastcgi module.

src/http/modules/ngx_http_fastcgi_module.c

diff --git a/src/http/modules/ngx_http_fastcgi_module.c b/src/http/modules/ngx_http_fastcgi_module.c
index c30e663..6f639ac 100644
--- a/src/http/modules/ngx_http_fastcgi_module.c
+++ b/src/http/modules/ngx_http_fastcgi_module.c
@@ -1744,8 +1744,10 @@
         }
 
         if (p->free) {
-            b = p->free->buf;
-            p->free = p->free->next;
+            cl = p->free;
+            b = cl->buf;
+            p->free = cl->next;
+            ngx_free_chain(p->pool, cl);
 
         } else {
             b = ngx_alloc_buf(p->pool);