Merge pull request #410 from frankrolf/master

Do not create empty guidelines array

Author: benkiel

Diff for: Lib/defcon/objects/font.py

@@ -1060,6 +1060,8 @@ def _get_identifiers(self):
     def _get_guidelines(self):
         if self._info is None:
             self.info
+        if not self._guidelines:
+            return None
         return list(self._guidelines)
 
     def _set_guidelines(self, value):