Improve Spark Lines to Handle Data Gaps

[vkoves]

The spark lines added in PR #116 works great 95% of the time, but with buildings with data gaps, like Willis tower, it doesn't perform draw a line, and only shows the min and max points, and then dots on hover.

We should also consider some way of adding tests for this component, whether Vitetest unit tests, a page with some randomly generated data, or both.