`ctx.drawImage` can throw exception if somehow `imgs` is invalid and hence will no longer render UI

### Expected Behavior

Gracefully handle such case. The reason is images can corrupt when connection suddenly disconnect, hence will make the image corrupted, and `drawImage` will refuse to draw it.

Problematic line:

https://github.com/comfyanonymous/ComfyUI/blob/e2382b6adb70c65416f3e90a168cbbc5ffe491bd/web/scripts/app.js#L788

### Actual Behavior

UI stopped rendering when having corrupted image.

### Other

I think simply wrap the line around `try catch` should be enough.