Structure blocks can not save structures

Structure names can only have lowercase alphanumeric and _ - .

Confirmed for 18w22c.

Structure blocks do not save, unless you hit the save button twice. May have to do with the fact that it updates the name with minecraft:<structure_name>, only after pressing save once.

Another note: when using relative coordinates in the save structure block (instead of manually placing a corner block), it is unable to detect the structure. This wasn't the case before, as I have used that feature to maximize my saving, without having to count blocks.