Automatic merge from submit-queue (batch tested with PRs 43653, 43654, 43652)
CRI: Check nil pointer to avoid kubelet panic.
When working on the containerd kubernetes integration, I casually returns an empty `sandboxStatus.Linux{}`, but it cause kubelet to panic.
This won't happen when runtime returns valid data, but we should not make the assumption here.
/cc @yujuhong @feiskyer