[Bug]: ControlNet mask not working

### Checklist

- [X] The issue exists after disabling all extensions
- [X] The issue exists on a clean installation of webui
- [ ] The issue is caused by an extension, but I believe it is caused by a bug in the webui
- [ ] The issue exists in the current version of the webui
- [X] The issue has not been reported before recently
- [ ] The issue has been reported before but has not been fixed yet

### What happened?

The 'Use mask' option for ControlNet doesn't do anything, I added a black & white mask image, even tried painting, and it has no effect on the output.

### Steps to reproduce the problem

Click on Use mask in ControlNet ui, add a mask or draw one. You will see it doesn't have any effect whatsoever.

### What should have happened?

It should've worked.

### What browsers do you use to access the UI ?

Brave

### Sysinfo

N/A

### Console logs

```Shell
N/A
```

### Additional information

_No response_

Start by reproducing the issue in a clean installation through the ControlNet UI, using both an uploaded black-and-white mask and a drawn mask. Compare outputs with and without “Use mask”; the fix is complete when the mask visibly changes the generated result and the behavior is covered by a suitable regression check.

Written by the indexing model from the issue text.