list: fix {flags:<WIDTH>} formatting, fixes #6081

item.bsdflags is either not present or an int, thus we default to 0 (== no flags) if not present.

src/borg/helpers.py

@@ -2051,7 +2051,7 @@ class ItemFormatter(BaseFormatter):
             item_data['health'] = 'broken' if 'chunks_healthy' in item else 'healthy'
         item_data['source'] = source
         item_data['linktarget'] = source
-        item_data['flags'] = item.get('bsdflags')
+        item_data['flags'] = item.get('bsdflags', 0)
         for key in self.used_call_keys:
             item_data[key] = self.call_keys[key](item)
         return item_data