@ -86,7 +86,7 @@ class _AutoapiInheritanceGraph(sphinx.ext.inheritance_diagram.InheritanceGraph):
tooltip = '"%s"' % doc.replace('"', '\\"')
baselist = []
all_classes[cls] = (nodename, fullname, baselist, tooltip)
all_classes[cls] = (nodename, fullname, baselist, tooltip or "")
if fullname in top_classes:
return