[test] Extend a test of destructuring.

R=adamk@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2147733003
Cr-Commit-Position: refs/heads/master@{#37773}

test/mjsunit/regress/regress-5178.js

@@ -5,3 +5,5 @@
 assertThrows(() => {
   try { throw {} } catch({a=b, b}) { a+b }
 }, ReferenceError);
+
+try { throw {a: 42} } catch({a, b=a}) { assertEquals(42, b) };