Fix typo of theme
Fix typo of theme

This was giving a warning that we couldn't get a font from undefined.

Contributes to issue CURA-3161.

fieldOfView/Cura,Curahelper/Cura,fieldOfView/Cura,hmflash/Cura,ynotstartups/Wanhao,Curahelper/Cura,ynotstartups/Wanhao,hmflash/Cura