[TYPO3-templavoila] non-mapped columns show in backend

[Albert Dekker]

In the DS I have defined various "content areas" such as Main Content 
and left Content.
Based on the DS I have mapped the only the Main Content.
nevertheless in the backend also a column for the Left Content is 
showing up whereas I did not map it.

Is this related to the "bug" which was mentioned in the thread started 
on 30 May by Stephan Petzl "not mapped fields get not shown in page 
module".
How could I get rid of this additional column.
Regards,
Albert