We could definitely add some error handling for this.

The bindings that call this function are created from the same layout strings used to generate layouts, so when we check if the layout class exists, we could prevent the binding from being created (and log) if the layout class doesn't exist.  

Since those bindings are the only places this function is called, that would ideally prevent NSNotFound from ever being returned unless the user inserted code to mangle the layouts array after it was created or to call this function with a bad class.