Some comboboxes in tool settings hidden for small window; do not appear in drop-down menu

Steps to reproduce:

• open Inkscape with Mint Y as the Gtk Theme
• go to Pen tool

What happened?

Shape combobox is not visible in the Pen toolbar except with BSpline path

See that in video, the dropdown was visible initially, but disappeared on restart. Didn't want to clean up my desktop so I trimmed out the restart from the video.

theme

What should have happened?

Always present regardless of mode. Note correct behaviour happens in Mint X, Adwaita, Adwaita dark (and Raleigh and Win32 but they are unusable on my system)

Inkscape Version and Operating System:

Issue introduced in b8e9f23d (at least on my system, with this test case). and present on Inkscape 1.0beta1 (2b9eeffa, 2019-10-24) Linux Mint 19.1.