NULLs needed at fail_pending_writes() too

src/core/ext/transport/chttp2/transport/chttp2_transport.c

@@ -1523,13 +1523,17 @@ static void fail_pending_writes(grpc_exec_ctx *exec_ctx,
                                 grpc_error *error) {
   error =
       removal_error(error, s, "Pending writes failed due to stream closure");
-  s->fetching_send_message = NULL;
+  s->send_initial_metadata = NULL;
   grpc_chttp2_complete_closure_step(
       exec_ctx, t, s, &s->send_initial_metadata_finished, GRPC_ERROR_REF(error),
       "send_initial_metadata_finished");
+
+  s->send_trailing_metadata = NULL;
   grpc_chttp2_complete_closure_step(
       exec_ctx, t, s, &s->send_trailing_metadata_finished,
       GRPC_ERROR_REF(error), "send_trailing_metadata_finished");
+
+  s->fetching_send_message = NULL;
   grpc_chttp2_complete_closure_step(
       exec_ctx, t, s, &s->fetching_send_message_finished, GRPC_ERROR_REF(error),
       "fetching_send_message_finished");