Steps to reproduce:
- Start GanttProject and load a project
- Hide columns “Begin date” and “End date” for example
- Save project and close GanttProject
- Restart GanttProject and reload the project
- Modify an item
- Press “Ctrl-N” to create a new project
- When the warning popup appears, click “Cancel” or press “Esc”.
- The “Begin date” and “End date” are now shown.
This could be the symptom of something deeper.