edit a doc hit enter to insert a break (this causes a split) backspace (this causes a join) undo twice redo twice sometimes, the above steps crash. The problem is that split and join aren't setting the selection correctly after the operation, so we sometimes operate on content data that is no longer in the tree.

I have the fix for this. It has very low risk, no new interfaces or dependancies. Suggest we get it in for M3 on the branch after a code review.

fixed.

verified in 3/19 build.