appease mypy, drop official release from dfns.toml (only nightly build has the dfns asset for now)

Author: wpbonelli

modflow_devtools/dfn/schema.py

@@ -754,7 +754,10 @@ def get_fields(dfn: Dfn) -> OMD:
 
 def _has_grid_dependent_shapes(dfn: Dfn) -> bool:
     """Return True if any field uses a semicolon grid-type-dependent shape."""
-    for block in dfn.get("blocks", {}).values():
+    blocks = dfn.get("blocks", {})
+    if not blocks:
+        return False
+    for block in blocks.values():
         for field in block.values():
             if ";" in str(field.get("shape") or ""):
                 return True

modflow_devtools/dfns/dfns.toml

@@ -4,6 +4,6 @@
 #   - Windows: %APPDATA%/modflow-devtools/dfns.toml
 
 releases = [
-    "MODFLOW-ORG/modflow6@latest",
+    # "MODFLOW-ORG/modflow6@latest",
     "MODFLOW-ORG/modflow6-nightly-build@latest"
 ]