Problem when changing subpree ports

[IgorAlvesSilva]

When a port is added or removed from a subtree using groot and the file is saved the subtree disappears.

[MHantzsch]

I had a similar problem, where Groot crashes and erases the content of a subtree. The subtree itself with its ports was still defined, but the structure of the subtree was erased. Unlike @IgorAlvesSilva i could not pinpoint a trigger for this to happen. For some context: I upgraded to the current master branch, which is when the crashes started to appear. A switch to the ver_3 branch avoids the problem, at least for me.