loader: Fix extraneous error log on Cilium startup
loader: Fix extraneous error log on Cilium startup

On startup, Cilium would always print the following error because we
didn't check that the error was nil before forming an `os.PathError()`.
Fix it:

  level=error msg="Unable to restore previous BPF templates"
  error="%!v(PANIC=runtime error: invalid memory address or nil pointer
  dereference)" subsys=daemon

Reported-by: Ian Vernon <57a33a5496950fec8433e4dd83347673459dcdfc@cilium.io>
Signed-off-by: Joe Stringer <16a9a54ddf4259952e3c118c763138e83693d7fd@cilium.io>

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