fix: handle empty boardType in get_device_property() to improve error handling

src/SingleShotAO.cpp

@@ -797,7 +797,7 @@ void SingleShotAO::get_device_property()
 
 	//- <BoardType> -----------------------
 	// Case 1 (error): boardType is set to the default value in the database
-	if (boardType == boardType_default)
+	if (boardType == boardType_default || boardType == "")
 	{
 		errorMessages << "Device property <BoardType> is not set (default value " << boardType_default << " needs to be replaced)" << endl;
 		critical_properties_missing = true;