[modules] Add tests for empty imports.

test/mjsunit/modules-skip-empty-import-aux.js

Index: test/mjsunit/modules-skip-empty-import-aux.js
diff --git a/test/message/arrow-invalid-rest-2.js b/test/mjsunit/modules-skip-empty-import-aux.js
similarity index 73%
copy from test/message/arrow-invalid-rest-2.js
copy to test/mjsunit/modules-skip-empty-import-aux.js
index 3517803d30256b09e78a1aa1f43817e733dc060e..1eb5b1515946c429ad9e28436d7c88c4e10804b0 100644
--- a/test/message/arrow-invalid-rest-2.js
+++ b/test/mjsunit/modules-skip-empty-import-aux.js
@@ -1,8 +1,6 @@
 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-//
-//
 
-var f = (a, ...x = 10) => x;
-f(1, 2, 3, 4, 5);
+export let counter = 0;
+export function incr() { counter++ };