[minigraph.py]: Fix undefined variable error. (#4555)

Signed-off-by: SuvarnaMeenakshi <[email protected]>

Author: SuvarnaMeenakshi

src/sonic-config-engine/minigraph.py

@@ -748,7 +748,7 @@ def parse_xml(filename, platform=None, port_config_file=None, asic_name=None):
             elif child.tag == str(QName(ns, "PngDec")):
                 (neighbors, devices, console_dev, console_port, mgmt_dev, mgmt_port, port_speed_png, console_ports) = parse_png(child, hostname)
             elif child.tag == str(QName(ns, "UngDec")):
-                (u_neighbors, u_devices, _, _, _, _, _, _) = parse_png(child, device_hostname)
+                (u_neighbors, u_devices, _, _, _, _, _, _) = parse_png(child, hostname)
             elif child.tag == str(QName(ns, "MetadataDeclaration")):
                 (syslog_servers, dhcp_servers, ntp_servers, tacacs_servers, mgmt_routes, erspan_dst, deployment_id, region) = parse_meta(child, hostname)
             elif child.tag == str(QName(ns, "DeviceInfos")):