Fixed the issue where colors same as text color turn black

This was because they are not stored and thus loaded as invalid colors,
which is fine, but on saving the invalid colors would then turn into
black.

Reviewed-by: Roberto Raggi

src/plugins/texteditor/colorscheme.cpp

@@ -151,7 +151,8 @@ bool ColorScheme::save(const QString &fileName)
         const Format &format = i.next().value();
         w.writeStartElement(QLatin1String("style"));
         w.writeAttribute(QLatin1String("name"), i.key());
-        if (i.key() == QLatin1String(Constants::C_TEXT) || format.foreground() != textFormat.foreground())
+        if (format.foreground().isValid() &&
+            (i.key() == QLatin1String(Constants::C_TEXT) || format.foreground() != textFormat.foreground()))
             w.writeAttribute(QLatin1String("foreground"), format.foreground().name().toLower());
         if (format.background().isValid())
             w.writeAttribute(QLatin1String("background"), format.background().name().toLower());