fix v1.1 mapper bugs

Author: wpbonelli

modflow_devtools/dfn/mapper.py

@@ -39,6 +39,6 @@ def map(dfn: v1.Dfn) -> v1.Dfn:
         for field_name, field_data in block_fields.items():
             dfn[block_name][field_name] = field_data  # type: ignore[literal-required]
 
-    dfn["blocks"] = blocks if blocks else None
+    dfn["blocks"] = None  # cleared; _serialize_safe drops None, blocks are now top-level keys
     dfn["schema_version"] = "1.1"
     return dfn

modflow_devtools/dfn/schema.py

@@ -855,9 +855,10 @@ def to_flat(dfn: Dfn) -> Dfns:
     """Flatten a hierarchical definition into its constituent definitions."""
 
     def _to_flat(_dfn: Dfn) -> Dfns:
+        children = dict(_dfn.get("children") or {})
         result: Dfns = {_dfn["name"]: _dfn}
         result[_dfn["name"]]["children"] = None
-        for child in (_dfn["children"] or {}).values():
+        for child in children.values():
             result.update(_to_flat(child))
         return result