pie: emit `plotly_hover` even if hoverinfo is none
pie: emit `plotly_hover` even if hoverinfo is none

Fixes https://github.com/plotly/plotly.js/issues/902

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