use isFallbackError cond

Author: huozhi

packages/next/src/server/route-modules/pages/pages-handler.ts

@@ -692,8 +692,15 @@ export const getHandler = ({
 
         // when invoking _error before pages/500 we don't actually
         // send the _error response - only skip if customErrorRender is set
-        // (meaning pages/500 exists and will be rendered next)
-        if (getRequestMeta(req, 'customErrorRender')) {
+        // (meaning pages/500 exists and will be rendered next), or if using
+        // the builtin _error in minimalMode to allow error bubbling
+        if (
+          getRequestMeta(req, 'customErrorRender') ||
+          (isErrorPage &&
+            isMinimalMode &&
+            res.statusCode === 500 &&
+            !isFallbackError)
+        ) {
           return null
         }