Fix XML generation for attribute-less boxes

diff --git a/src/nepi/util/parser/base.py b/src/nepi/util/parser/base.py
index 58bd6ed..1737f14 100644 (file)
--- a/src/nepi/util/parser/base.py
+++ b/src/nepi/util/parser/base.py
@@ -218,6 +218,7 @@ class ExperimentParser(object):
                 g_info.height, g_info.label)
 
     def factory_attributes_to_data(self, data, guid, factory_attributes):
+        factory_attributes = factory_attributes or dict()
         for name, value in factory_attributes.iteritems():
             data.add_factory_attribute_data(guid, name, value)