helptext_building() assumes that nukes have tech requirement
/* TRANS: 'Allows all players with knowledge of atomic
* power to build nuclear units.' */
_("%s Allows all players with knowledge of %s "
"to build %s units.\n"), BULLET,
That doesn't consider the possibility that the unit has no (valid) tech requirement. I don't think the effects would be more dire than funny texts ("...knowledge of Never to build...")