I was inspecting my application with Google Chrome and kept getting this error “Uncaught TypeError: Cannot read property ‘substring’ of undefined at HTMLDivElement.<anonymous>”. So … spent some time going back through things and could not find it. So I started over with a brand new treemenu with nothing on it - that’s where it is coming from.
To reproduce:
Create a new treemenu
Put 1 item with 2 subitems on it (they don’t even have to attach to an application - just text in the label field)
Run it on Google Chrome - Right click and choose “Inspect”
Expand & collapse the menu items - watch the error repeat over and over again