Cleanup: remove all Q_NULLPTR instances

It expands to nullptr anyway and is inconsitent with the rest of the
code. Let's remove this anachronism.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

profile-widget/tankitem.cpp

@@ -31,7 +31,7 @@ TankItem::TankItem(QObject *parent) :
 	trimixGradient.setColorAt(1.0, red);
 	trimix = trimixGradient;
 	air = blue;
-	hAxis = Q_NULLPTR;
+	hAxis = nullptr;
 	memset(&diveCylinderStore, 0, sizeof(diveCylinderStore));
 }