Core: fixed buffer overrun when hash max_size reached.

src/core/ngx_hash.c

diff --git a/src/core/ngx_hash.c b/src/core/ngx_hash.c
index c7bfed7..65ad839 100644
--- a/src/core/ngx_hash.c
+++ b/src/core/ngx_hash.c
@@ -312,6 +312,8 @@
         continue;
     }
 
+    size--;
+
     ngx_log_error(NGX_LOG_WARN, hinit->pool->log, 0,
                   "could not build optimal %s, you should increase "
                   "either %s_max_size: %i or %s_bucket_size: %i; "