Notice: Trying to get property of non-object in node_page_title()

The book nav ToC widget was showing errors like this:

Notice: Trying to get property of non-object in node_page_title()

I have created a patch file so that "bootstrap/templates/book/book-navigation.vars.php" is not included so that this error goes away. I realize that you don't want this as part of the baseline and that is why I have marked this issue as closed.