Merge #3474

3474: Fix scrollbar going out of bounce (fixes #3416) r=Learath2 a=def-

<!-- What is the motivation for the changes of this pull request -->

## Checklist

- [x] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test if it works standalone, system.c especially
- [x] Considered possible null pointers and out of bounds array indexing
- [x] Changed no physics that affect existing maps
- [ ] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: def <dennis@felsin9.de>

src/game/client/components/menus_demo.cpp

@@ -570,7 +570,7 @@ void CMenus::UiDoListboxStart(const void *pID, const CUIRect *pRect, float RowHe
 	}
 
 	Scroll.HMargin(5.0f, &Scroll);
-	gs_ListBoxScrollValue = clamp(DoScrollbarV(pID, &Scroll, gs_ListBoxScrollValue), 0.0f, 1.0f);
+	gs_ListBoxScrollValue = clamp(DoScrollbarV(pID, &Scroll, clamp(gs_ListBoxScrollValue, 0.0f, 1.0f)), 0.0f, 1.0f);
 
 	// the list
 	gs_ListBoxView = gs_ListBoxOriginalView;