Fix for fatal error with --override-chars-to-quote

git-svn-id: http://svn.savannah.nongnu.org/svn/rdiff-backup@672 2b77aa54-bcbc-44c9-a7ec-4f6cf2b41109

trunk/rdiff-backup/rdiff_backup/fs_abilities.py

@@ -513,6 +513,7 @@ class BackupSetGlobals(SetGlobals):
 			log.Log("Warning: File system no longer needs quoting, "
 					"but we will retain for backwards compatibility.", 2)
 			return actual_ctq
+		if Globals.chars_to_quote is None:
 			log.Log.FatalError("""New quoting requirements!
 
 The quoting chars this session needs (%s) do not match