CalChart on Mac crashes when last continuity for any dot type is deleted

[pikybar]

If there is a list of continuities for any dot type, the program crashes if the bottom one is deleted, but deleting any other continuity from the list works fine.

[pikybar]

In v3.7.2 it would ask to save before crashing but in v3.8.0 it crashes immediately

[rmpowell77]

Thanks for filing this. Able to reproduce.

[rmpowell77]

Fixed in #659