Drop down menu in forms generate warnings and sometimes breaks selection
Context: !96 (comment 2029683)
Now the drop-down menus are fixed, but there seems to be some issues related to them. We get warnings of the form
(papers:476302): Gtk-WARNING **: 09:26:27.228: Broken accounting of active state for widget 0x61ddcc425d80(GtkComboBox)
And sometimes selection while the drop-down is opened gets into some issues, and the document gets into some kind of auto-scrolling behavior. It's not completely trivial to reproduce, but usually happens after clicking the drop down a couple of times, and moving the cursor while on it.