Small issue in ValueTree

When performing ‘addChild()’ as an undoable action, the insert index is only actually clamped if it is negative.
If it is greater than the number of existing children, this larger value is stored as-is in the undoable action, triggering an assert.

[if I make sure the insert index is safe manually, it works fine]

Sorry if you’ve fixed this already, I’m not really in a position to get the latest from git, and the zipped modules haven’t been updated for ages!

Cheers, I’ll tidy that up!