e655243825
When region is too small, `calculate_grid_step()` can return value of 0.
This can happen if the editor happens to be just few px wider than side panel.
The root cause was, that region pixelsize was calculated with
`BLI_rcti_size_x(&v2d->mask)`, but the result needs to be offset by 1.
Caused by ab43c57a2a
Pull Request: https://projects.blender.org/blender/blender/pulls/146365