test-runner: check if baseline img exist before px comparison
test-runner: check if baseline img exist before px comparison

iongroup/plotly.js,plotly/plotly.js,asolagmbh/plotly.js,aburato/plotly.js,plotly/plotly.js,asolagmbh/plotly.js,plotly/plotly.js,etpinard/plotly.js,etpinard/plotly.js,aburato/plotly.js,iongroup/plotly.js,iongroup/plotly.js,asolagmbh/plotly.js,etpinard/plotly.js,plotly/plotly.js