fixed K8S connection creation issue when kubeconfig or kubeconfig_path is empty string

[enniomorricone123]

When connection is defined from web UI all "extra" values get empty string for un-set values.

But in k8s hook we make decisions based on is not None.

These two ways of handling the values are incompatible. So we change to truthy evaluation here.

closes: #20626

[boring-cyborg]

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[potiuk]

I think there are some test cases covering already - could you please add a test case covering this case? sounds like an easy one

[enniomorricone123]

I think there are some test cases covering already - could you please add a test case covering this case? sounds like an easy one

yes, will do

[eladkal]

@enniomorricone123 Why did you close the PR? was it by mistake?

[dstandish]

this was resolved by #19695