operator: fix panic for non existing CEPs
operator: fix panic for non existing CEPs

```
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x118 pc=0x1dcb219]
goroutine 161 [running]:
main.enableUnmanagedKubeDNSController.func1(0x28aa1a0, 0xc00069e880, 0x3d3d0a0, 0xd9fc43ebeec50347)
	/go/src/github.com/cilium/cilium/operator/k8s_pod_controller.go:67 +0xa69
github.com/cilium/cilium/pkg/controller.(*Controller).runController(0xc000789a00)
	/go/src/github.com/cilium/cilium/pkg/controller/controller.go:205 +0xa2a
created by github.com/cilium/cilium/pkg/controller.(*Manager).updateController
	/go/src/github.com/cilium/cilium/pkg/controller/manager.go:120 +0xb09
```

Fixes: 26e74511a8dc ("operator: use watcher to track unmanaged pods")
Reported-by: Tobias Klauser <9249c549618448e4c699e8032ba6c7f0d7fd4b7f@distanz.ch>
Signed-off-by: André Martins <bc9800b9d52a24cce72a73dd528afed53f10e5fc@cilium.io>

tklauser/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,michi-covalent/cilium,cilium-team/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,cilium-team/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium