Hi @rogemer,
This issue could occur when you are testing with a work item without a tag. However, the trigger condition should prevent the flow from even triggering. So, it is odd that you are even getting a flow run, it shouldn't trigger in the first place.
How are you testing? Are you updating a work item in Azure DevOps and looking at the flow history?
Or are you using the Test feature of flow with a previous run and re-running it? With the latter you could run into this issue.