Web Inspector: exception in front-end on selecting an element in heap snapshot

Web Inspector: exception in front-end on selecting an element in heap snapshot
https://bugs.webkit.org/show_bug.cgi?id=79447

Fixed a typo in method name and added a check that selected node has
corresponding heap snapshot object before adding that object to the console
as $0 entry.

Reviewed by Pavel Feldman.

* inspector/front-end/DetailedHeapshotView.js:
(WebInspector.DetailedHeapshotView.prototype._inspectedObjectChanged):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108743 268f45cc-cd09-0410-ab3c-d52691b4dbfc