Caused by 5ed14e9269.
That commit accidentally removed the `copy_v2_v2_int(t->mval, mval);`
line which was responsible for initializing the value of `mval`.
In the 3D View, after navigating, the initial cursor position was
updated based on the relative position of the cursor in 3D space.
Now the initial relative position is maintained but moved closer to or
further from the 2d center based on zoom.
In order to avoid navigation hotkey conflicts during transform
operations, this commit implements the "Transform Navigation with Alt"
option.
This option is enabled by default and makes navigation hotkeys require
the `Alt` key during a transforming in the 3D View.
Pull Request: https://projects.blender.org/blender/blender/pulls/109754
