CNI bridge: `failed (add): failed to set bridge addr: could not set bridge's mac: invalid argument`

### Description

I do not have a simple reproducer for this.

This is just regularly popping up with custom deployment tooling as part of a large plan.

```
sudo nerdctl container run -d --name dns --hostname dns-magnetar.local --read-only --restart always --cap-add NET_BIND_SERVICE --env LOG_LEVEL=info --env DNS_STUFF_MDNS=false --network hadron-bridge --publish 4242:4242/tcp --volume data-dns:/magnetar/user/data --label org.hadron.core.version=v0.1-dev --label org.hadron.plan.description=some_plan_descriptor --label org.hadron.plan.name=plan_name --label org.hadron.plan.sha=7841eb9910d7b9d49f49e5940a73ca9d9a0dd6c4975640fd5eea4b39f5376744 --label org.hadron.plan.tag=2025/05/22-14:06:09-2EF02181-EF3C-4E68-9218-3C66599DC459 dubodubonduponey/dns:bookworm-2024-09-01

failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: error during container init: error running createRuntime hook #0: exit status 1, stdout: , stderr: time=\"2025-05-22T14:06:52-07:00\" level=fatal msg=\"failed to call cni.Setup: plugin type=\\\"bridge\\\" failed (add): failed to set bridge addr: could not set bridge's mac: invalid argument\""
```

Network is:
```
{
"cniVersion": "1.0.0",
"name": "hadron-bridge",
"nerdctlID": "f510b1557a7a8a34b10de53d186d9f44ae3ac06983994403aae8364fb6e4c6b6",
"nerdctlLabels": {
"org.hadron.core.version": "v0.1-dev",
"org.hadron.plan.description": "some_plan_descriptor",
"org.hadron.plan.name": "plan_name",
"org.hadron.plan.sha": "cae39eec27f94285311914ffe6af492685fd5b162ef41c7f55fdbd8e75183138",
"org.hadron.plan.tag": "2025/05/20-17:15:29-CC9CCD90-E6ED-4735-B34D-5570D3431248"
},
"plugins": [
{
"type": "bridge",
"bridge": "br-f510b1557a7a",
"isGateway": true,
"ipMasq": true,
"hairpinMode": true,
"ipam": {
"ranges": [
[
{
"gateway": "10.4.1.1",
"subnet": "10.4.1.0/24"
}
]
],
"routes": [
{
"dst": "0.0.0.0/0"
}
],
"type": "host-local"
}
},
{
"type": "portmap",
"capabilities": {
"portMappings": true
}
},
{
"type": "firewall",
"ingressPolicy": "same-bridge"
},
{
"type": "tuning"
}
]
}
```

The error comes (obviously) from CNI bridge (`func ensureAddr(br netlink.Link, family int, ipn *net.IPNet, forceAddress bool) error {`), and suggests that `netlink.Attrs` in certain circumstances fails to produce an actual hardware addr.

### Steps to reproduce the issue

na

### Describe the results you received and expected

Work.

### What version of nerdctl are you using?

main

### Are you using a variant of nerdctl? (e.g., Rancher Desktop)

None

### Host information

_No response_