When starting a VM with an installer which cannot be used unattended, I get this assertion. Such VMs start fullscreen

This assertion comes from the can_grab_mouse test in DisplayPage::update_toolbar_visible() which is called in response to a window state event (I assume this comes in reaction to the fullscreening). However, at this point DisplayPage::show_display hasn't been called, so DisplayPage::display is NULL, so display::can_grab_mouse cannot be checked.
display is only set later from a timeout callback set in a callback for display::show in Machine::display.

Not really sure what to do about all of this though...