Steps to reproduce:
- In VE standalone, edit <ul><li>X</li><li>Y</li></ul> .
- Put the cursor just after Y (on the same line), and use the toolbar to turn off the bulleting
Observed behaviour: ve.ce.ContentBranchNode#onTeardown throws an exception because this.root is null.
Expected behaviour: The unbulleting works without an exception.
The TreeModifier change would naturally be the prime suspect, and indeed the broken behaviour was introduced by 37d1512a74bd51038fd837656beb065aa0564d7e .