[Geary] Theme in 3.34

[Axel U <ulrich axel gmail com>]

I have been running Geary via flatpak for a while now.  I just ran flatpak update, and as expected it updated the runtime, Gnome, etc. including moving Geary up to 3.34.0.  I am running a fundamentally dark theme on my desktop, and Geary obeyed that so far.  But with the upgrade, it went to a light grey/white theme that doesn't match anything else on my desktop.  Not sure where it gets that information from to use said colors, because before it simply followed the rest of the desktop scheme.  I am only running Geary via flatpak, so I could not tell if this also suddenly applies to other apps run via flatpak.  Why is that and how to get it to obey the color scheme again like it did before?  Running on Fedora F30.

Axel