Graph lines are cut off incorrectly

[hackerb9]

Graph lines are being pruned when they should not be. This is the flipside to #218 which describes extra lines being added to a graph.

For example, consider the function made famous by the movie Mean Girls,

$$\lim_{x\to 0^+}{{\ln(1-x) - \sin x}\over{1 - \cos^2 x}}$$

[hackerb9]

For comparison, this is how the graph is supposed to look (as rendered by Desmos):