QLabel::setPixmap() isn't virtual, don't make it so.

src/libcalamaresui/widgets/FixedAspectRatioLabel.h

@@ -1,6 +1,7 @@
 /* === This file is part of Calamares - <http://github.com/calamares> ===
  *
  *   Copyright 2015, Teo Mrnjavac <teo@kde.org>
+ *   Copyright 2017, Adriaan de Groot <groot@kde.org>
  *
  *   Calamares is free software: you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -30,7 +31,7 @@ public:
     virtual ~FixedAspectRatioLabel();
 
 public slots:
-    virtual void setPixmap( const QPixmap &pixmap );
+    void setPixmap( const QPixmap &pixmap );
     void resizeEvent( QResizeEvent* event ) override;
 
 private: