Reviewed by Kevin.

    Reviewed by Kevin.

	<rdar://problem/3935390> Tiger 8A341: nil deref crash in DOM::NodeImpl::traverseNextNode

	* khtml/html/html_miscimpl.cpp:
        (HTMLCollectionImpl::traverseNextItem): Assert that the starting point is not nil,
	it should not ever be (now).
        (HTMLCollectionImpl::item): When traversing items stop when we hit
	nil, meaning the end to avoid triggering above assert (formerly crash).

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8289 268f45cc-cd09-0410-ab3c-d52691b4dbfc