Don't fail if no dry-run setting has been specified

Somehow we failed if no dry-run setting had been specified in the config
file. This got caught thanks to extending the test suite with a stock
configuration.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

Changelog.rst

@@ -17,6 +17,9 @@ Changes
 Bug Fixes
 ---------
 
+* Don't fail if no dry-run setting exists in offlineimap.conf
+  (introduced in 6.5.3)
+
 
 OfflineIMAP v6.5.3 (2012-04-02)
 ===============================

offlineimap/ui/UIBase.py

@@ -49,7 +49,7 @@ class UIBase(object):
     def __init__(self, config, loglevel = logging.INFO):
         self.config = config
         # Is this a 'dryrun'?
-        self.dryrun = config.getboolean('general', 'dry-run')
+        self.dryrun = config.getdefaultboolean('general', 'dry-run', False)
         self.debuglist = []
         """list of debugtypes we are supposed to log"""
         self.debugmessages = {}