Vega or Vega Lite in Deneb generates the following error "Cannot read properties of null (reading 'marktype')"

Question

I´ve run in the problem in Vega and Vega Lite that I couldn´t generate a signal that needs a field from data.

Example:

    {
      "name": "summeSignal",
      "update": "data('dataset')[0]['row']"
    }

The same happend if I tried to calculate values in marks or signals without using a defined signal.

I tried reducing the datasets, putting the signal block on other positions in the json in the hope that this maybe a parsing problem and I tried to acces data that isn´t ready yet.

That sadly did nothing for me.

EDIT:

I found two workarounds that helped.

1. adding a value to the dataset provided by powerBi: {"name": "dataset", "values": {"category": "test"}}

But that didn´t allways do the trick.

2. trigger the update with a timer event: { "name": "signal", "init": "0", "on": [ { "events": [ { "type": "timer", "throttle": 500 } ], "update": "data('dataset')[0]['row']" } ] }

If there is a trigger for a data refresh or change that could be a more elegant solution, but I didn´t found any.