Cannot set CIRCLE_RADIUS=0

The usefulness of setting CIRCLE_RADIUS=0 is mentioned in the Circle Mode page and is a good thing to be able to do.
However, in Standard Parameters in MP (and in DroidPlanner), it can be set no lower than 1.
It can be set in the full parameter list, though.

Can the validation for that value box in standard parameters please be updated to allow zero?

please do a MP update, and it should allow a 0 entry.