It seems that every time I edit an issue, I have to select one of the priorities. I'd rather leave the priority blank and clear it to some issues that accidentally got a priority. Is there a way to do that?
As far as I can see, Priority is marked as optional:

but I don't have a blank option that I can select:

I don't want to hide the field as I might want to use it, but even if I hide the field, some issues already have a priority and they appear as a small icon (a green down arrow here):
