[Gimp-gui] The interface displays incorrect characters because of different themes.

[兰欣悠 <stiywy gmail com>]

Hello,

　　The interface displays incorrect characters because of different themes.

　　Only under the system theme, the display is correct.

　　When using other themes, the characters are not displayed correctly. The language is Simplified Chinese. Windows 10.

　　Thanks to the developer for their efforts.

　　Screenshot below，