ENH: Adding earlier exception, which makes debugging easier.

src/caosadvancedtools/json_schema_exporter.py

@@ -258,7 +258,8 @@ class JsonSchemaExporter:
         schema : dict
             A dict containing the json schema created from the given RecordType's properties.
         """
-
+        if rt is None:
+            raise ValueError("`rt` must not be None.")
         schema = self._make_segment_from_recordtype(rt)
         schema["$schema"] = "https://json-schema.org/draft/2019-09/schema"
         if rt.name: