HTTP/2: improved error handling while parsing integers.

The case when an integer is out of frame bounds should be checked first
as a more accurate error.

src/http/v2/ngx_http_v2.c

diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
index 5852c99..91f7bc9 100644
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -2417,14 +2417,14 @@
         }
     }
 
-    if (end == start + NGX_HTTP_V2_INT_OCTETS) {
-        return NGX_DECLINED;
-    }
-
     if ((size_t) (end - start) >= h2c->state.length) {
         return NGX_ERROR;
     }
 
+    if (end == start + NGX_HTTP_V2_INT_OCTETS) {
+        return NGX_DECLINED;
+    }
+
     return NGX_AGAIN;
 }