I'm having the same problem, except ABSEAL_AUTOKILL is already on TRUE so that can't solve it.
I'm using Blizz ABS 1.98, I've got the three sections of the script in three different slots, so my scripts look like Scene_Debug // ABS1 // ABS2 // ABS3 // Main.
My error message is:
Script 'ABS3' line 3658: NoMethodError occurred.
undefined method 'color' for nil:NilClass
although sometimes its line 3661 instead. I've set up the enemies so that when a switch gets triggered, they appear. However, if an untriggered enemy is within range when I try and use a skill, it errors.
Any ideas?