Stop clicks on the globe from changing dive list selection while editing

This caused us to get royally confused when manually adding a dive and
trying to set the location through the marble widget.

Fixes # 229

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/maintab.h

@@ -58,6 +58,7 @@ public:
 	bool eventFilter(QObject* , QEvent*);
 	void initialUiSetup();
 	void equipmentPlusUpdate();
+	bool isEditing();
 public slots:
 	void addCylinder_clicked();
 	void addWeight_clicked();