Fixes #683: Fix crash when rendering WirelessLink without label

[ray34g]

Summary

This PR fixes a crash when enabling "Show Wireless Links" in the topology view.

Problem

When "Show Wireless Links" is enabled, NetBox Topology Views can raise:

AttributeError: 'WirelessLink' object has no attribute 'label'

This happens because WirelessLink objects do not have a label attribute,
but the topology view code assumes its existence.

Fix

Guard access to label using hasattr and only render the label when it exists.
This avoids the AttributeError while preserving existing behavior for Cable.

Tested

• NetBox v4.4.7 (Community)
• netbox-topology-views v4.4.0
• Kubernetes deployment with custom NetBox image to use the plugin

Fixes #683