fix: normalize mark object like primitive mark. (#7260)
fix: normalize mark object like primitive mark. (#7260)

Fixes #7257
uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,vega/vega-lite,uwdata/vega-lite,vega/vega-lite,vega/vega-lite,vega/vega-lite,uwdata/vega-lite,uwdata/vega-lite