Fix windows warning C26478 - Don't use `std::move` on constant variables

[DanRStevens]

Use a reference to work around buggy MSVC warning:

OPHD\libControls\ScrollBar.cpp(250): error C26478: Don't use std::move on constant variables.

Example problem run: https://github.com/OutpostUniverse/OPHD/actions/runs/7684040546

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The original code perhaps makes slightly more sense, but has been generating a warning with recent MSVC compiler releases. A fix has supposedly been released, but doesn't seem to be present on GitHub Action runners.

References:

• https://stackoverflow.com/questions/77051369/msvc-gives-warning-c26478-using-stdmove-on-constant-variables
• https://developercommunity.visualstudio.com/t/Wrong-C26478-warning-when-using-structur/10417562

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Related to Issue #307