Initialize m_cupsCodec

Ensure initialization of m_cupsCodec to nullptr. The codec is checking
the value of m_cupsCodec; but the initialization was conditional before
this patch.

Change-Id: I81751b7743e9956f31f17cead01dc05e268db7eb
Coverity-Id: 188700
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

src/printsupport/dialogs/qprintdialog_unix.cpp

@@ -154,7 +154,7 @@ private:
     bool anyAdvancedOptionConflict() const;
 
     QPrintDevice *m_currentPrintDevice;
-    QTextCodec *m_cupsCodec;
+    QTextCodec *m_cupsCodec = nullptr;
     QVector<QComboBox*> m_advancedOptionsCombos;
 #endif
 };