gin: Bug fix: Fix CreateHandle to return an emtpy handle in some extreme cases

In some extreme cases, ObjectTemplate::NewInstance might return an empty
handler. For example, the getter and setter
Object.prototype.constructor can be rewritten with a evil function which
can throw exceptions.

BUG=331301
TEST=gin_unittests --gtest_filter=WrappableTest.ErrorInObjectConstructorProperty

Review URL: https://codereview.chromium.org/184253004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254109 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254109