Keyboard shortcuts to change line height do not work with new preferences

Steps to reproduce:

• open Inkscape
• type a (normal) text with multiple lines
• Use Ctrl + Alt + < and Ctrl + Alt + > to adjust the line height (https://inkscape.org/doc/keys.html#idm3518)

What happened?

• This works for me in 0.92.x, but it does nothing in master.

What should have happened?

• Line height should have changed (even though, with a German keyboard, Shift seems to be counted twice, so I get small steps with the 'reduce' option, and large steps with the 'grow' option, as the < and > symbol are on the same key).

• as soon as the line height option has been changed once (e.g. to adjustable), the shortcut works in all future cases (thank you to @nathanal for testing and finding that out!)

Inkscape Version and Operating System:

• Inkscape Version: 1.0alpha (083f7eab9b, 2019-04-03)
• Operating System: Linux Mint 19.1