Move drawing area to another drawing

[HeikoKlare]

When moving a drawing area (copy or cut and paste) to another drawing, the drawing becomes broken. Not only that the moved drawing area cannot be used properly, there are even workflows that lead to a crash of the complete application:

1. Create a drawing area
2. Copy the drawing area into a new drawing
3. Create another drawing area in the new drawing (both will exist then)
4. Save and close the new drawing
5. Reload the drawing (a message telling you that the drawing area cannot be found will show up)
6. Create a new drawing area
7. An access violation error will occur.

Copying drawing areas to other drawing should either be properly supported or, more likely as this functionality is not really needed, trying to copy them should be rejected.