Modding

You forgot to change the mapobject for the goblin.

I think the game crashes simply because of an error in the city building file; maybe you accidentally removed an extra character or added an extra line.

Or maybe it crashes because of the Yeti; there might be some error in its code.

P. S.
You didn't list everything that's also tied to goblins. What about Keagan's special ability, the goblin-devouring ability, and goblin sacrifices? Also, now, on maps with garrisons that have goblins already stationed, there will be goblins instead of Yetis.

Added 3 minutes later
CREATURE_SNOW_APE, I think; you should check that.

Only "CREATURE" was changed in the building; you need to check your version – that might be the reason.

I didn't list the other abilities to avoid unnecessary text.
*Keagan's special ability is now "Master of Mercenaries" – it works normally, as does everything else. It's all simply tied to "a regular goblin and all its subsequent upgrades, if any."
*For example, goblin sacrifices, in addition to the customizable mana coefficient (which can actually be zero), also have a buff to attack and defense (and morale), which stacks several times, and all of this can also be customized for specific values. I was considering implementing such a mechanic for some of the "Dark Dawn" creatures – for example, Liches, who could sacrifice mercenaries and increase their ATK/DF by (+5), and this could stack up to 5 times (as an option)