Search logger is called without being initialized

[yleflour]

I noticed that in the Search class, if debug=False (which is by default), the client fails to handle some errors.

This is because:

• If debug=False, self.logger==None
• While some calls to logger.debug() checks for self.debug == True, some lines in _backoff() don't and directly call logger.debug()
• This causes the library to raise an uncaught error

PS: Thank you so much for this library which is finally allowing me to export my bookmarks properly