EE 7.4.11
When a Category is set to not allow multiple selections, and thus uses a radio button, you cannot unselect that button if you decide you want to leave that category blank for that entry.
Current workaround is to edit that Channel's Category to Allow Multiple Selections, return to entry and un-check checkbox, then return to category settings and toggle Allow Multiple Selections back to the off position.
EE 7.4.11
When a Category is set to not allow multiple selections, and thus uses a radio button, you cannot unselect that button if you decide you want to leave that category blank for that entry.
Current workaround is to edit that Channel's Category to Allow Multiple Selections, return to entry and un-check checkbox, then return to category settings and toggle Allow Multiple Selections back to the off position.