nixos-render-docs: don't validate redirects if non were given

pkgs/by-name/ni/nixos-render-docs/src/nixos_render_docs/redirects.py

@@ -87,6 +87,10 @@ def validate(self, initial_xref_targets: dict[str, XrefTarget]):
           - Identifiers must not be identical to any historical location's anchor of the same output path
           - The first element of an identifier's redirects list must denote its current location.
         """
+        # Disable redirects validation if redirects were not provided
+        if not self._raw_redirects:
+            return
+
         xref_targets = {}
         ignored_identifier_patterns = ("opt-", "auto-generated-", "function-library-")
         for id, target in initial_xref_targets.items():