Calypso Browser is getting grey when removed from Window group

[astares]

When I open a Pharo window (like Playground) and select "Create window group" I can drag and drop other windows onto it. So one can group several windows into one, each one shown with a tab.

This works for most of the Pharo windows (Playground, Iceberg, ...) in latest P7 - but not for the Calypso browser.

I can drag a system browser into the window group - but when I drag it out again it is just a gray window and the content is not usable anymore.

I guess this is a bug in Calypso.

[astares]

See also http://lists.pharo.org/pipermail/pharo-dev_lists.pharo.org/2018-June/272268.html