Stop null-checking the pres shell so that we get to the UnbindFromTree call in nsHTMLEditor::DeleteRefToAnonymousNode. (Bug 563980) r=ehsan

editor/libeditor/html/nsHTMLAbsPosition.cpp

@@ -313,7 +313,9 @@ nsHTMLEditor::HideGrabber()
 
   // get the presshell's document observer interface.
   nsCOMPtr<nsIPresShell> ps = do_QueryReferent(mPresShellWeak);
-  if (!ps) return NS_ERROR_NOT_INITIALIZED;
+  // We allow the pres shell to be null; when it is, we presume there
+  // are no document observers to notify, but we still want to
+  // UnbindFromTree.
 
   nsCOMPtr<nsIDOMNode> parentNode;
   res = mGrabber->GetParentNode(getter_AddRefs(parentNode));