align resource and pure data source schema with regular schema

dlt/extract/extract.py

@@ -75,8 +75,9 @@ def choose_schema() -> Schema:
         """Except of explicitly passed schema, use a clone that will get discarded if extraction fails"""
         if schema:
             schema_ = schema
+        # if we have a default schema name, use it but do not collect any info from the existing schema
         elif pipeline.default_schema_name:
-            schema_ = pipeline.schemas[pipeline.default_schema_name].clone()
+            schema_ = Schema(pipeline.default_schema_name)
         else:
             schema_ = pipeline._make_schema_with_default_name()
         return schema_