ipam: Fix SIGSEGV when accessing n.resource
ipam: Fix SIGSEGV when accessing n.resource

It is possible for the IP deficit resolution to be triggered before the
initial CiliumNode resource is asigned to the node. n.resource can be
nil in this scenario.

Fixes: #10582

Signed-off-by: Thomas Graf <5f50a84c1fa3bcff146405017f36aec1a10a9e38@cilium.io>

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