No default scheduling folder for account 'Local Folders' could be determined

Since a couple of weeks (I think after, adding gmail calendar) everytime I start up Em client, I get this message:
no default scheduling folder for account ‘Local Folders’ could be determined.

I searched the forum and found this solution :

 Go to Menu > Accounts and click on the General tab.
 Scroll down to Default Folders.
 Select a calendar.
 Click on Save & Close.

But in my case it is not a solution, because ‘Local folder’ does not show up in Accounts.
Any other ideas?