Can't modify stroke width of multi-series sparkline chart

[lmansur]

Description

Passing a two-element array to stroke.width while using a two-series sparkline chart breaks the rendering of the chart. It seems related to this commit, specifically the part where math is being performed on stroke.width, even though it might be an array(L54-L56): 2ac1adb

Steps to Reproduce

1. Create a two-series sparkline chart
2. Add two values for stroke.width, like [2, 3]

Expected Behavior

Render each series with the given stroke width

Actual Behavior

The chart can't be rendered

Screenshots

When not specifying the stroke width:

When specifying a two-element array stroke width:

Reproduction Link

https://codepen.io/lmansur/pen/mdojgWm?editors=1111