handle config.json failed to load

[w-e-w]

Description

shows a error like this and rever default if config.json failed to load as opposed to crash
issue #14521

*** Could not load settings
*** The config file "B:\Stable Diffusion\Configs\config.json" is likely corrupted
*** It has been moved to the "tmp/config.json"
*** Reverting config to default
***
    Traceback (most recent call last):
      File "B:\GitHub\stable-diffusion-webui\modules\launch_utils.py", line 250, in list_extensions
        settings = json.load(file)
      File "C:\Programs\Python\3.10.6\lib\json\__init__.py", line 293, in load
        return loads(fp.read(),
      File "C:\Programs\Python\3.10.6\lib\json\__init__.py", line 346, in loads
        return _default_decoder.decode(s)
      File "C:\Programs\Python\3.10.6\lib\json\decoder.py", line 337, in decode
        obj, end = self.raw_decode(s, idx=_w(s, 0).end())
      File "C:\Programs\Python\3.10.6\lib\json\decoder.py", line 353, in raw_decode
        obj, end = self.scan_once(s, idx)
    json.decoder.JSONDecodeError: Expecting ',' delimiter: line 300 column 32 (char 10686)

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