24.061 Loading mod IRobot 1.1.2 (data-final-fixes.lua)
24.064 Error ModManager.cpp:1577: Failed to load mod "IRobot": IRobot/data-final-fixes.lua:45: attempt to index global 'char' (a nil value)
stack traceback:
IRobot/data-final-fixes.lua:45: in main chunk

This is with angels/bob mods and a bunch more. Nothing that deals with extra characters.

--- IRobot_1.1.2/data-final-fixes.lua~ 2021-09-30 19:30:33.000000000 +0200
+++ IRobot_1.1.2/data-final-fixes.lua 2021-10-02 14:32:31.091599522 +0200
@@ -42,7 +42,7 @@
if replace_base_char then
-- Overwrite vanilla character
IROBOT.writeDebug("Overwriting base character with \"%s\".", {CHAR_NAME})
- chars["character"] = table.deepcopy(char[CHAR_NAME])
+ chars["character"] = table.deepcopy(chars[CHAR_NAME])
new_char = chars["character"]

-- Make adjustments to new character

Thanks for the report! Such a stupid typo … :-)