When undocking the ColorMapEditor, QVTKOpenGLSimpleWidget become black until hovered

When undocking the ColorMapEditor, QVTKOpenGLSimpleWidget become black until hovered

How to reproduce :

Open ParaView
Sources->Wavelet, Apply
Color by RTData
Show color map editor
Undock color map editor
QVTKOpenGLSimpleWidget based widget become black
Over mouse on the widgets
QVTKOpenGLSimpleWidget based widget become ok again

NOT related to !2471 (merged)

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