FIX: Net.extended_net returns first ExtendedNet object

Author: chenchienjacklin

src/ansys/edb/core/net/net.py

@@ -117,5 +117,8 @@ def extended_net(self):
 
         This property is read-only.
         """
-        en = self._layout_objs(LayoutObjType.NET_CLASS)[0]
+        en = self._layout_objs(LayoutObjType.EXTENDED_NET)
+        if not en:
+            return None
+        en = en[0]
         return None if en.is_null else en