GH-1556 do not crash when instance has no update task while creating an instance

application/dialogs/ProgressDialog.cpp

@@ -17,6 +17,7 @@
 #include "ui_ProgressDialog.h"
 
 #include <QKeyEvent>
+#include <QDebug>
 
 #include "tasks/Task.h"
 
@@ -57,6 +58,12 @@ int ProgressDialog::execWithTask(Task *task)
 	this->task = task;
 	QDialog::DialogCode result;
 
+	if(!task)
+	{
+		qDebug() << "Programmer error: progress dialog created with null task.";
+		return Accepted;
+	}
+
 	if(handleImmediateResult(result))
 	{
 		return result;