Certain fonts cannot be selected via UI, but do work with StreamController #172

Describe the bug
Certain fonts appear to be available when formatting a Label, but are not actually selected by the UI, and are not written to corresponding page config file. Manually editing the JSON file for the page may allow such fonts to be employed - there seems to be a visual change of some kind. This is for version 1.5.0-beta.6, tested on Ubuntu 24.04, default GNOME on X.

To Reproduce
Steps to reproduce the behavior:

1. Click on a blank button,
2. Enter a string for a label,
3. Click on the font selection button,
4. Select font from resulting dialog (for example, Work Sans Bold), either by double-clicking on the font name, or by single-clicking on the font name and then clicking on "Select",
5. A different font is actually selected (in this example, Work Sans Regular).

Expected behavior
Fonts should be selected correctly.

Screenshots
For example, selecting this font, shown here:

...actually selects Work Sans Regular, aka Work Sans, and produces this config snippet:
"labels": { "center": { "text": "Test", "font-family": "Work Sans", "font-size": 18.0 }

Additional context
The issue appears to have something to do with some fonts having more than two words in their name. For example, if the above snippet is manually modified to:

"labels": { "center": { "text": "Test", "font-family": "Work Sans SemiBold", "font-size": 18.0 }

..a different font is used after app restart, as shown here:

It isn't clear whether the correct font is being employed, but something different is: