Handle empty k8s version in existing profile

[afbjorklund]

Fixes #6291

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: afbjorklund

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[codecov-io]

Codecov Report

Merging #6292 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #6292   +/-   ##
=======================================
  Coverage   38.28%   38.28%           
=======================================
  Files         124      124           
  Lines        8257     8257           
=======================================
  Hits         3161     3161           
  Misses       4686     4686           
  Partials      410      410

Impacted Files	Coverage Δ
cmd/minikube/cmd/start.go	22.03% <100%> (ø)	⬆️

[sharifelgamal]

/ok-to-test

[minikube-bot]

All Times Minikube (PR 6292): [ 125.700559 111.029539 113.866473]
All Times minikube: [ 124.011131 124.005956 124.272921]

Average minikube: 124.096669
Average Minikube (PR 6292): 116.865523

Averages Time Per Log

+----------------------+-----------+--------------------+
|         LOG          | MINIKUBE  | MINIKUBE (PR 6292) |
+----------------------+-----------+--------------------+
| minikube v           |  0.460113 |           0.408210 |
| Creating kvm2        | 47.138752 |          46.240212 |
| Preparing Kubernetes | 50.490941 |          44.826703 |
| Pulling images       |  3.396616 |           2.636312 |
| Launching Kubernetes | 19.999320 |          19.993081 |
| Waiting for cluster  |  2.566196 |           2.718007 |
| Done                 |           |                    |
|                      |  0.045155 |           0.046172 |
+----------------------+-----------+--------------------+