A scrollbar button would be cast to a number-slider button, and values from
this memory used for scrollbar specific calculations. Looks like an error from
809499a3d0.
In practice the error wouldn't be visible, since the actually used value would
by chance be the intended value, from what I can tell. That's because
`uiButNumberSlider.step_size` and `uiButScrollBar.visual_height` have the same
memory offset within the button memory.
f86c042724