[KConfigGui] Check font weight when clearing styleName property

Summary:
This is an addendum for commit a2774ff5b41987c3919a9e; making the check
tighter.

Test Plan: make && ctest

Reviewers: #frameworks, dfaure, davidedmundson, cfeck, ervin, meven, bport

Reviewed By: dfaure

Subscribers: kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D27811

src/gui/kconfiggroupgui.cpp

@@ -161,10 +161,11 @@ static bool writeEntryGui(KConfigGroup *cg, const char *key, const QVariant &pro
         // than the former. For more details see:
         // https://bugreports.qt.io/browse/QTBUG-63792
         // https://bugs.kde.org/show_bug.cgi?id=378523
-        if (f.styleName() == QLatin1String("Regular")
+        if (f.weight() == QFont::Normal
+            && (f.styleName() == QLatin1String("Regular")
             || f.styleName() == QLatin1String("Normal")
             || f.styleName() == QLatin1String("Book")
-            || f.styleName() == QLatin1String("Roman")) {
+            || f.styleName() == QLatin1String("Roman"))) {
             f.setStyleName(QString());
         }
         cg->writeEntry(key, f.toString().toUtf8(), pFlags);