bug: errors creating OperationStarted event

[krancour]

I've noticed quite a few error messages of this form in my logs today:

time="2024-05-15T20:42:03Z" level=error msg="unable to create \"OperationStarted\" event for Argo CD Application: an empty namespace may not be set during creation" app=kargo-demo-02-uat freight=9fa6593491e062616ac5358e9c2f5ef1befc9583 namespace=kargo-demo-02 promotion=uat.01hxyzv6h110dppk0vdgz4jcjz.9fa6593 stage=uat

@hiddeco mind taking a look? I think this came in with #1848