Don't delete it. If the game calls something that doesn't exist you can expect it to die.
But if you open them up (any text editor will do) and remove everything except forCreature_type: CREATURE_HERO;
#Start_group_settings
#End_group_settings
#Start_Bone_data
#End_bone_data
for all of the Hero's bones, it will completely remove bone morphing. You could also change all the numbers to about 0.9 or 1.0 and you'll get a similar effect, 0.9 making him a tad smaller.
The alternative is deleting the bone entries in the CHeroMorphDef. That makes it so the Hero doesn't use the bones at all.