KConfig will clear the styleName font property for "Regular"-like font
styles (so that setBold(true) can work properly); this means that when
opening the font selection dialog it may highlight the wrong style for
the font currently set in kdeglobals, i.e. if the styleName property is
empty, QFontDialog will always select the first style in the list.
Workaround the issue by setting the "Regular"-like font style of the
adjustAllFonts() doesn't take any arguments, change the QML code accordingly.
See also https://phabricator.kde.org/D27735 (KConfig)