I noticed the same problem with the macOS build when I tested meson - I assumed it was something with meson and wanted investigate later but it's probably something different.
When launched from the command-line, I get lots of messages like this: ``` (geany:33653): Gtk-WARNING **: 21:32:36.763: Error loading theme icon 'document-open' for stock: Icon 'document-open' not present in theme Adwaita ``` Appears to be this
https://gitlab.gnome.org/GNOME/adwaita-icon-theme/-/issues/184
and the linked GTK issue.