client.interactive: fix error when interface_classes empty

Change-Id: I7a4f3052d4c666186930b3b6dceca5f18d89d4e3
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/31078
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

frappy/client/interactive.py

@@ -123,7 +123,7 @@ class Module:
         self._running = None
         self._status = None
         props = secnode.modules[name]['properties']
-        self._title = f"# {props.get('implementation', '')} ({props.get('interface_classes', [''])[0]})"
+        self._title = f"# {props.get('implementation', '')} ({(props.get('interface_classes') or ['Module'])[0]})"
 
     def _one_line(self, pname, minwid=0):
         """return <module>.<param> = <value> truncated to one line"""