Dashed Line Not Working Properly

* [x] I've read, understood, and done my best to follow the [*CONTRIBUTING guidelines](https://github.com/jjatie/Charts/blob/master/CONTRIBUTING.md).

## What did you do?

Plotting a dashed line in a line chart not working properly. See image:

There are 365 points per data set. Those that are close to each other don't reflect the dashed line. as you can see on the red line, I intentionally dropped one of the points to have a Y of zero so that it will show the dashed line. The blue and pink line don't appear dashed.

## What did you expect to happen?

Dashed line should reflect

## What happened instead?

See above

## Charts Environment

**Charts version/Branch/Commit Number:**
3.3.0
**Xcode version:**
10.2.1
**Swift version:**
5.0
**Platform(s) running Charts:**
iPhone
**macOS version running Xcode:**
10.14.6

## Demo Project

[Archive.zip](https://github.com/danielgindi/Charts/files/3532935/Archive.zip)

I did it on the ChartsiOS Demo version. Please see MultipleLinesChartViewController.swift

Start with MultipleLinesChartViewController.swift in the linked demo project and reproduce the dashed-line case using the provided archive and the reported Charts 3.3.0 environment. Compare lines whose points are close together with the red line containing a zero value; done means dashed styling is visibly preserved for all plotted lines.

Written by the indexing model from the issue text.