do not render empty strings and lists
@@ -93,6 +93,7 @@ class ExtraFieldsMixin(metaclass=MediaDefiningClass):
"""Enrich list of CSS classes with customized ones"""
css_classes = super().get_css_classes(obj)
extra_css_classes = obj.glossary.get('extra_css_classes')
+ if extra_css_classes:
if isinstance(extra_css_classes, str):
css_classes.append(extra_css_classes)
elif isinstance(extra_css_classes, (list, tuple)):
