QWinRTFontDatabase: Return the base class' fallbacksForFamily

instead of an empty list.
Even if QBasicFontDatabase::fallbacksForFamily() returns an empty list ;)

Change-Id: Ib4a63e7898d2708737dd694f0629bdb68b2eb3a1
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

src/plugins/platforms/winrt/qwinrtfontdatabase.cpp

@@ -439,6 +439,7 @@ QStringList QWinRTFontDatabase::fallbacksForFamily(const QString &family, QFont:
     QStringList result;
     if (family == QLatin1String("Helvetica"))
         result.append(QStringLiteral("Arial"));
+    result.append(QBasicFontDatabase::fallbacksForFamily(family, style, styleHint, script));
     return result;
 }