Solution for failed image generation in SD Forge and openoutpaint extension.

[bkrew]

This could also solve Problems in other aspects as it is quite a universal failsafe.
Possible fix for TypeError: argument of type 'NoneType' is not iterable in Stable Diffusion Forge with openOutpaint
Problem description

When generating images with the openOutpaint extension in Stable Diffusion WebUI Forge, I ran into the following error:

Total progress: 25%|██▌ | 30/120 [00:01<00:05, 16.23it/s]s] 
ERROR: Exception in ASGI application
Traceback (most recent call last):
  ...
  File "D:\StabilityMatrix\Packages\Stable Diffusion WebUI Forge\modules\processing.py", line 1405, in sample
    if hasattr(self, 'hr_additional_modules') and 'Use same choices' not in self.hr_additional_modules:
TypeError: argument of type 'NoneType' is not iterable

Likely cause

The error seems to come from modules/processing.py (line 1405).
It looks like the code applies not in to self.hr_additional_modules, which can sometimes be None instead of an iterable (list or string).

Workaround / change

I tested adding a simple null check to avoid applying the operator on None.

Original code:

if hasattr(self, 'hr_additional_modules') and 'Use same choices' not in self.hr_additional_modules:

Modified code:

if hasattr(self, 'hr_additional_modules') and self.hr_additional_modules is not None and 'Use same choices' not in self.hr_additional_modules:

Notes

This adjustment prevents the crash in my case.

I haven’t tested this thoroughly with other extensions or all Forge features yet.

It might be worth reviewing if there are other spots where hr_additional_modules can be None.

[gnomeby]

You can also pass
hr_additional_modules: [],
in request to prevent this error