F delete container

https://gitlab.com/caosdb/caosdb-pylib/-/merge_requests/61

src/caosdb/common/models.py

@@ -2820,12 +2820,15 @@ class Container(list):
                         has_references.add(references.value)
                     elif is_list_datatype(references.datatype):
                         for list_item in references.value:
-                            if isinstance(list_item, int): 
+                            if isinstance(list_item, int):
                                 has_references.add(list_item)
                             else:
                                 has_references.add(list_item.id)
                     else:
-                        has_references.add(references.value.id)
+                        try:
+                            has_references.add(references.value.id)
+                        except:
+                            pass
 
         dependent_parents = item_id.intersection(is_parent)
         dependent_references = item_id.intersection(has_references)