Potential fix for code scanning alert no. 67: Explicit returns mixed with implicit (fall through) returns

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: deeplook

src/svglib/svglib.py

@@ -956,7 +956,7 @@ def renderUse(
         self.renderNode(list(node.iter_children())[-1], parent=group)
         self.apply_node_attr_to_group(node, group)
         return group
-
+        return None
 
 class SvgShapeConverter:
     """An abstract SVG shape converter.