[GREENFOOT-774] Importing or duplicating a class creates strange state

In an arbitrary scenario with all classes compiled, go to Import Class... then import a class, e.g. the Map class. When you click OK on the Import window, do nothing else. The scenario shows the world greyed out, and Act/Run/Reset disabled. All existing classes are compiled, Map is not. It's fairly easy to fix the state: defocusing then refocusing the window works, or manually creating a new world instance. But it's a bit puzzling as I thought I was waiting for it to compile Map, but actually nothing was happening.

Edit: duplicating a class does exactly the same thing. Duplicate a world class, and the new copy is uncompiled, but all the exec controls are greyed out and the world is greyed out, until you open an editor for the class or defocus/refocus the window.

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Issue metadata

• Issue type: Task
• Priority: Medium