Inpaint only mask switch to img2img if mask is blank

[w-e-w]

Description

@storyicon

• This is an alternative implementation of a "part" of what Fix images do not match / Coordinate 'right' is less than 'left' #15534 is trying to achieve

when performing Inpaint with only mask mode if the mask is blank (as in there's nothing to inpaint)
currently web UI would throw an error

ValueError: Coordinate 'right' is less than 'left'

Fundamentally there is no real issue during this error because there's nothing to do, but the message bit cryptic
they might even be a minor beneficial as in it stops unnecessary processing
but it could also be disrupted when you're doing a batch job scenario

so this is an alternative limitation that would instead perform normal img2img if the mask is blank

implemented using a try block as I think this makes the code more readable

if ValueError ever occurred performs img2img and shows a message

'Unable to perform "Inpaint Only mask" because mask is blank, switch to img2img mode.'

---

in this PR I did not implement resizing of self.mask_for_overlay

unless my analysis is incorrect
that piece of code would only ever be triggered when performing Inpaint Only mask with a mask size different from the input image
if resizeing is peformed to the mask like in #15534, the resulting output would only be an inpaint with misaligned mask, the misalignment can vary from a little to a lot depending on the mask size difference
which in my viewpoint just makes the output erratic so the results will be erratic

if mask resizing is to be implementm for Inpaint Only mask, it should be performed before cropping of the mask
the issue is there is a certain quirk about the WebUI that makes making this a bit awkward

when using webui img2img vial API, it is possible to have multiple input images but only have ONE mask image

I personally would think that there is no reason that you would use the same mask for multiple images but that's how the code is written

I think if we would want to support resizing of the input mask for Inpaint Only mask, we should make it possible to also input multiple mask image as well to make things consistent

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests

[AUTOMATIC1111]

merged the other one because it had a more specific check for the situation instead of the general exception

[w-e-w]

merged the other one because it had a more specific check for the situation instead of the general exception

I would argue that value error is very specific as this isthe behavior of PIL.Image.corp

https://github.com/python-pillow/Pillow/blob/5c89d88eee199ba53f64581ea39b6a1bc52feb1a/src/PIL/Image.py#L1219-L1240

        if box[2] < box[0]:
            msg = "Coordinate 'right' is less than 'left'"
            raise ValueError(msg)
        elif box[3] < box[1]:
            msg = "Coordinate 'lower' is less than 'upper'"
            raise ValueError(msg)