Fix #10460

[dongweiming]

Describe what this pull request is trying to achieve.

If i uncheck the checkbox "Save metadata (.safetensors only"), this error will be reported:

Loading /Users/weiming.dong/workspace/stable-diffusion-webui/models/Stable-diffusion/CounterfeitV30_v30.safetensors...
Loading /Users/weiming.dong/workspace/stable-diffusion-webui/models/Stable-diffusion/AnythingV5_v5PrtRE.safetensors...
Merging...
100%|██████████████████████████████████████████████████████████████████████████████████████████| 1133/1133 [00:02<00:00, 429.50it/s]
Saving to /Users/weiming.dong/workspace/stable-diffusion-webui/models/Stable-diffusion/0.85(AnythingV5_v5PrtRE) + 0.15(CounterfeitV30_v30).safetensors...
Error loading/saving model file:
Traceback (most recent call last):
  File "/Users/weiming.dong/workspace/stable-diffusion-webui/modules/ui.py", line 1719, in modelmerger
    results = modules.extras.run_modelmerger(*args)
  File "/Users/weiming.dong/workspace/stable-diffusion-webui/modules/extras.py", line 285, in run_modelmerger
    safetensors.torch.save_file(theta_0, output_modelname, metadata=metadata)
  File "/Users/weiming.dong/workspace/stable-diffusion-webui/venv/lib/python3.10/site-packages/safetensors/torch.py", line 232, in save_file
    serialize_file(_flatten(tensors), filename, metadata=metadata)
TypeError: argument 'metadata': 'dict' object cannot be converted to 'PyString'

I fixed this error: #10460

Environment this was tested in

List the environment you have developed / tested this on. As per the contributing page, changes should be able to work on Windows out of the box.

• OS: Mac M1
• Browser: chrome, safari

This is required for anything that touches the user interface.

[AUTOMATIC1111]

the problem seems bigger than that and also you save metadata regardless of whether the user has enabled it via the checkbox

[dongweiming]

the problem seems bigger than that and also you save metadata regardless of whether the user has enabled it via the checkbox

How about this? i saw the default value of metadata is None

[AUTOMATIC1111]

yeah and I was also incorrect about the problem being bigger, everything's fine

[dongweiming]

I'm glad I could help~

[cvar66]

Issue is still happening