Added info notification, when Color Change G-code is empty and user try to add color change on DoubleSlider.

src/slic3r/GUI/NotificationManager.hpp

@@ -65,7 +65,9 @@ enum class NotificationType
 	// Object fully outside the print volume, or extrusion outside the print volume. Slicing is not disabled.
 	PlaterWarning,
 	// Progress bar instead of text.
-	ProgressBar
+	ProgressBar,
+	// Notification, when Color Change G-code is empty and user try to add color change on DoubleSlider.
+	EmptyColorChangeCode
 };
 
 class NotificationManager
@@ -453,6 +455,9 @@ private:
 			if (evnthndlr != nullptr) wxPostEvent(evnthndlr, PresetUpdateAvailableClickedEvent(EVT_PRESET_UPDATE_AVAILABLE_CLICKED)); return true; }},
 		{NotificationType::NewAppAvailable, NotificationLevel::ImportantNotification, 20,  _u8L("New version is available."),  _u8L("See Releases page."), [](wxEvtHandler* evnthndlr){ 
 				wxLaunchDefaultBrowser("https://github.com/prusa3d/PrusaSlicer/releases"); return true; }},
+		{NotificationType::EmptyColorChangeCode, NotificationLevel::RegularNotification, 10,  
+			_u8L("You have just added a G-code for color change, but its value is empty.\n"
+				 "To export the G-code correctly, check the \"Color Change G-code\" in \"Printer Settings > Custom G-code\"") },
 		//{NotificationType::NewAppAvailable, NotificationLevel::ImportantNotification, 20,  _u8L("New vesion of PrusaSlicer is available.",  _u8L("Download page.") },
 		//{NotificationType::LoadingFailed, NotificationLevel::RegularNotification, 20,  _u8L("Loading of model has Failed") },
 		//{NotificationType::DeviceEjected, NotificationLevel::RegularNotification, 10,  _u8L("Removable device has been safely ejected")} // if we want changeble text (like here name of device), we need to do it as CustomNotification