Line plot nicely handle empty data

[asizemore]

Lots of variables in the microbiome are sparse, so it's easy to make plots with no data :)

Here's one:

Some plots have a nice banner that says "no plottable data for the selection". Probably appropriate here as well?

[dmfalke]

Is this is a "Must have" for b62?

[asizemore]

Still an issue for line plot. To reproduce, pick any two Species-level variables. Likely they will have no overlap.

The scatterplot looks nice in this case. Can we do the same for the line plot?

[asizemore]

scatter example