Fix fuse_custom_config_dict arg from being None (#102154)
`fuse_custom_config_dict` in [fuse_modules.py](https://github.com/pytorch/pytorch/blob/main/torch/ao/quantization/fuse_modules.py#L164) being passed as None even if a fuse_custom_config_dict is provided.
This patch fixes the `fuse_custom_config_dict` from being passed as None.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102154
Approved by: https://github.com/kit1980
