We can apply the `V2D_KEEPZOOM` and `V2D_KEEPOFS_Y` flags to the main VSE
region to make sure this happens. If `V2D_KEEPZOOM` is set, we should update
the view2d's `oldwinx` and `oldwiny` in `ui_view2d_curRect_validate_resize`
just like the `V2D_KEEPASPECT` case.
Divide-by-zero is a real possibility here, since initialization status of
`oldwinx/y` cannot be determined from the `resize` boolean alone (e.g. loading
regions from disk on startup yields a `true` `resize` parameter, so any old
regions that have `KEEPZOOM` added through versioning will get this error since
their `oldwinx/y` is uninitialized). Avoid by initializing `oldwinx/y` if it is zero in
`ui_view2d_curRect_validate_resize`.
Addresses #136508.
Pull Request: https://projects.blender.org/blender/blender/pulls/137802
7d9499bdc4