BUG: Run Config overrides Kubernetes imagePullSecrets

[zhen0]

Bug Description

Context: for our k8s agents we have image pull secrets defined for the cluster so that flows don't need to provide their own in order to be able to pull images from the container registry. i.e. the job templates we provide to KubernetesRun config don't contain imagePullSecrets.
Problem: when submitting a job from UI with the Run button, if we don't touch the AdvancedConfiguration section, the configuration that gets passed to k8s has (eg flow run)
"image_pull_secrets": null,
But if the user opens the AdvancedConfiguration tab and than hits Run the configuration passed to k8s has (eg flow run)
"image_pull_secrets": []
This happens even if nothing is changed in AdvancedConfiguration. I.e. the sole action of opening the tab before hitting run results in this change. The result is disastrous because the null value does not override the cluster image pull secret default but the empty list does override it resulting in the pod being unable to pull the image.
Desired behavior: opening the AdvancedConfiguration and changing any of the settings should not produce a change in the image_pull_secrets settings (or any other setting for that matter that the user did not change)

Steps To Reproduce

Browsers Tested:

• Chrome
• Firefox
• Safari
• Edge
• IE

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Notes