Describe the bug
We have a pod with two containers
argocd-application-controller (no cpu limit)
linkerd-proxy (10m cpu limit)

To Reproduce

1. pods view
2. see a red percentage limit thing ...

   ┌────────────────────────────────────────────────────────────────── Pods(argocd)[18] ──────────────────────────────────────────────────────────────────┐
   │ NAME                                            READY RESTARTS STATUS   CPU MEM %CPU/R %MEM/R %CPU/L %MEM/L IP          NODE                         │
   │ argocd-application-controller-5f48755598-vclkf  2/2          0 Running   41 136     13     26    409      6 10.52.2.16  gke-default-cluster-default… │
   

3. See percentage that looks scary
4. highlight row
5. press enter
6. scroll right to see cpu/l

   ┌──────────────────────────────────────── Containers(argocd/argocd-application-controller-5f48755598-vclkf)[3] ────────────────────────────────────────┐
   │ READY  STATE       INIT     RESTARTS PROBES(L:R)   CPU  MEM  %CPU/R  %MEM/R   %CPU/L   %MEM/L PORTS                                    AGE           │
   │ true   Running     false           0 on:on          40  120      13      24        0        5 controller:8082                          5h46m         │
   │ true   Completed   true            0 off:off       n/a  n/a     n/a     n/a      n/a      n/a                                          5h46m         │
   │ true   Running     false           0 on:on           2   15      40      75       20       37 linkerd-proxy:4143,linkerd-admin:4191    5h46m         │
   

7. For perspective, check the output from kubectl:

   $ kubectl -n argocd top pod argocd-application-controller-5f48755598-vclkf
   NAME                                             CPU(cores)   MEMORY(bytes)
   argocd-application-controller-5f48755598-vclkf   112m         136Mi
   $ kubectl -n argocd get pod argocd-application-controller-5f48755598-vclkf -o json|jq -r -M '{unlimited_name: .spec.containers[0].name, unlimited_res:.spec.containers[0].resources, limited_name: .spec.containers[1].name, limited_res:.spec.containers[1].resources}'
   {
     "unlimited_name": "application-controller",
     "unlimited_res": {
       "limits": {
         "memory": "2Gi"
       },
       "requests": {
         "cpu": "300m",
         "memory": "500Mi"
       }
     },
     "limited_name": "linkerd-proxy",
     "limited_res": {
       "limits": {
         "cpu": "10m",
         "memory": "40Mi"
       },
       "requests": {
         "cpu": "5m",
         "memory": "20Mi"
       }
     }
   }

Expected behavior
Containers which have no limit (as this one does) should be treated as n/a, and skipped while summing numerators and denominators.

Screenshots

Versions (please complete the following information):

• OS: Mac OS 10.14.6
• K9s: 0.20.3
• K8s: v1.16.13-gke.401

Additional context