auto type conversion (#4270)
* type conversion
Default value of `control_guidance_start` and `control_guidance_end` in `StableDiffusionControlNetPipeline.check_inputs` causes `TypeError: object of type 'float' has no len()`
Proposed fix:
Convert `control_guidance_start` and `control_guidance_end` to list if float
* Update src/diffusers/pipelines/controlnet/pipeline_controlnet.py
* Update src/diffusers/pipelines/controlnet/pipeline_controlnet.py
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
* Update src/diffusers/pipelines/controlnet/pipeline_controlnet.py
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
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Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
