Mapbox "fitBounds" handling

As per https://github.com/plotly/plotly.R/blob/9ee548023bba6d68dd953f46485b2e611026766b/inst/htmlwidgets/plotly.js#L206-L220

I believe the if(!args) check should be changed (or the parameter for args should default to null or some other calculated default, not {}) as it currently causes an "e is undefined" error in mapbox (where e is the 2nd parameter).

I've got around it by explicitly providing a mapbox = list(_fitBounds = list(c(xmin, ymin), c(xmax, ymax)), options = list()) entry in my plotly::layout call.

This also serves as a reminder that the fitBounds doesn't seem to work for restyle either.

从 inst/htmlwidgets/plotly.js 的第 206–220 行开始，重点关注 fitBounds 参数的默认值，以及产生第二个参数为 undefined 错误的 Mapbox 调用。分别在有和没有显式 mapbox 选项列表的情况下复现该问题，然后验证 fitBounds 在 restyle 期间也能正常工作。