Debug screen FPS / TPS graphs are not rendered correctly

The bug

Since 1.15-pre4 the debug screen FPS / TPS graphs are not rendered correctly anymore:

• Min, max and average values are rendered behind the graph columns now
• The "30 FPS", "60 FPS" and "20 TPS" labels are gray (fixed in 1.15-pre5)
• MC-167105: Graphs behind hotbar, but apparently only when no item is selected in the hotbar