[GREENFOOT-469] Saving the world multiple times in succession doesn't work well

If you save the world in Greenfoot, it adds code to the world but does not seem to trigger a recompile.

Even if you do trigger a recompile, it seems like the save the world item on the menu gets into an odd state, where (on Linux) mousing over it does not show a highlight, and it cannot be clicked again.

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Issue metadata

• Issue type: Bug
• Priority: Medium
• Fix versions: 3.0.3