HTTP/2: fix handling of connection errors.

Previously, nginx worker would crash because of a double free
if client disconnected or timed out before sending all headers.

Found with afl-fuzz.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

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 51cf65a..32da12f 100644
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -2377,12 +2377,6 @@
         ngx_debug_point();
     }
 
-    if (h2c->state.stream) {
-        h2c->state.stream->out_closed = 1;
-        h2c->state.pool = NULL;
-        ngx_http_v2_close_stream(h2c->state.stream, NGX_HTTP_BAD_REQUEST);
-    }
-
     ngx_http_v2_finalize_connection(h2c, err);
 
     return NULL;
@@ -3814,6 +3808,12 @@
 
     c = h2c->connection;
 
+    if (h2c->state.stream) {
+        h2c->state.stream->out_closed = 1;
+        h2c->state.pool = NULL;
+        ngx_http_v2_close_stream(h2c->state.stream, NGX_HTTP_BAD_REQUEST);
+    }
+
     h2c->blocked = 1;
 
     if (!c->error && ngx_http_v2_send_goaway(h2c, status) != NGX_ERROR) {