Line graph not drawn for single data point

[zee0786]

I am trying to draw a line graph, but it fails to draw the graph if it has only one point to draw, except for the second last point.

please go through the following pen. In this pen I have made two samples of data, one that works an the other just doesn't.
Can somebody please help?

https://codepen.io/zee0786/pen/OJYxQBO?editors=0010