fix get_crop_region_v2

[w-e-w]

Description

@AUTOMATIC1111 I made a major syntactical error missed a preferences on my ternary operator

• https://github.com/AUTOMATIC1111/stable-diffusion-webui/issues/15593

Checklist:

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

[shanghailaofashi001]

When I generate an image, I am prompted with AttributeError: 'NoneType' object has no attribute 'lowvram'