Revo Uninstaller 1.95 from rapps initially does not draw the bitmap on a button

Reproduction steps

• download Revo Uninstaller 1.95 from rapps and start it
• select the second tab "Tools"

Expected result
The button should immediately have the bitmap drawn onto it
2k3sp2_ok.webm

Observed result
The button has no bitmap drawn initially
0.4.12-RC-50-geb1a43d_buttons.webm
0.4.12-RC-50-geb1a43d_buttons.log
But as soon as the window is moved offscreen and back, or the mouse cursor is wiggled over the button, the bitmap will be drawn.

The bug is old, I noticed it in every single release test since ros 0.4.0 already