BUG ID: Bugzilla bug 9466 Assertion failure when dragging an image from the document into Safari's address bar

1. Drag the apple image into this window’s address bar.
2. Choose History > Back to go back to this page.
3. Drag a URL from a TextEdit document into this window.

TEST PASS: In step 3, this window will accept the dragged URL.

TEST FAIL: In step 1, Safari will quit unexpectedly due to an assertion failure. Alternatively, in step 3, this window will not accept the dragged URL.