Hello,
I had previously reported a bug where a colonist ship would ask to load colonists aboard the colony ship endlessly if no colonists were available because the minimum amount was 0.5 as opposed to zero. The pop-up would keep showing up again and again even if you clicked "Cancel" . This original bug appears to have been fixed.
However:
I encountered a similar bug playing as Yor except that this time, there were colonists on my world. I had 12.1 million of them. Neither the ok nor the cancel button would get rid of this popup.
I had to close the game with Alt-F4, reload the game and cancel the colonist ship from my shipyard.
I also constructed a Transport vessel during this game at the same shipyard and it did not suffer from this bug.