[GREENFOOT-823] Scenario does not (always) open with double-click on project.greenfoot

Double-click on the project.greenfoot file should open a scenario.

This works if Greenfoot is not running, but if Greenfoot is already open, then the new scenario does not open correctly (process starts, but no window appears). (Observed on MacOS.)

Issue metadata

Issue type: Bug
Priority: Medium
Fix versions: 3.5.4