Here is what you have to do:
Open bi/ci/data/export_descr_character_traits.txt. Find those two triggers.
Code:
;------------------------------------------
Trigger fertile_tribe_of_the_craban_vnv_trigger
WhenToTest CharacterComesOfAge
Condition Trait TribeOfTheCraban >= 1
Affects Fertility 1 Chance 100
;------------------------------------------
Code:
;------------------------------------------
Trigger fertile_tribe_of_the_mighty_axe_vnv_trigger
WhenToTest CharacterComesOfAge
Condition Trait TribeOfTheMightyAxe >= 1
Affects Fertility 1 Chance 100
;------------------------------------------
Change the word "Fertility" to "Fertile".
Save and exit.
That's it, you will be able to go on with your game as usual.