Hate those dark themes 
Looks like a bug in the theme. Reproducing the effect.
Five screenshots in one, https://i.imgur.com/7eoK2Ug.jpg
1. The original path
2. Renamed path, newname barely visible.
3. You can see it if you make the main Gimp window inactive. That might mean something to a themes guru.
4. You can get it back with some editing on the canvas.
5. Toggled the path visibility on and the text returned to barely visible. Needed more editing on the canvas to get it back.
Post your report at https://gitlab.gnome.org/GNOME/gimp/issues/
Looks like a bug in the theme. Reproducing the effect.
Five screenshots in one, https://i.imgur.com/7eoK2Ug.jpg
1. The original path
2. Renamed path, newname barely visible.
3. You can see it if you make the main Gimp window inactive. That might mean something to a themes guru.
4. You can get it back with some editing on the canvas.
5. Toggled the path visibility on and the text returned to barely visible. Needed more editing on the canvas to get it back.
Post your report at https://gitlab.gnome.org/GNOME/gimp/issues/