Display gets messed up when routing panel is active

To reproduce with current Fedora 29 (with gnome-maps 3.30.1), just run Maps, right-click somewhere, and select 'Route from here'. The routing panel to the right of the map opens, but half of it is not visible, seemingly covered in some sort of odd white...layer. If you then resize the window, the whole routing panel disappears behind the white layer, and the window stops being square (the right hand side of the window sort of bleeds past the X button, is the best way I can describe it).

Additionally, if you then right-click anywhere and click 'What's Here?' after triggering the above bug, Maps crashes.

There's a video and a backtrace attached to the downstream bug.

Find recent F29 images at https://www.happyassassin.net/nightlies.html .