#78 expanddummy is not removed properly

[tobias.weih]

sometimes an xcp.Issue expands allthough it has no children, thus the clientside is to blame.
Issue will be organized hirachicaly soon, so implementing it by cripling the Issue to 'not expandable' in TreeBuilder is no solution.

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USECASE
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set the status of an Issue using the context-men?. e voila, le bug.