UnionSplitter shows error in Output Schema even though there are no errors from the backend

For the attached pipeline, when I open the UnionSplitter and click on validate, I get a green banner on the top saying there are no validation errors, but I also have an error message in the output schema. As a user, I am unsure whether I have an error or not. Also, I am unsure what this particular error message means .

Update: This error appears to be caused by the backend sending back a field with type null in the portSchemas when it should be sending back an error because the field being split is not of union type (see attachment).