NullPointerException while trying to access /charts

When i access url2jira/charts then i get NullPointerException.
This is caused by me not giving arguments to DisplayChartsServlet and in the source of DisplayChartServlet someone trying to create a java.io.File with null argument.

Error in log

2013-12-13 11:16:53,565 http-bio-8443-exec-25 ERROR      [500ErrorPage.jsp] Exception caught in 500 page null
java.lang.NullPointerException
	at java.io.File.<init>(File.java:291)
	at com.atlassian.jira.charts.jfreechart.DisplayChartServlet.service(DisplayChartServlet.java:61)

How to reproduce

1. In your own test jira
   1. go to address https://mylocaljira*/charts*
2. in Atlassians live jira (Caution, it pollutes your live logs with NPE-s)
   1. go to url https://jira.atlassian.com/charts

How to fix?

To fix that you should just add null check to com.atlassian.jira.charts.jfreechart.DisplayChartServlet

Affected versions

My affected system is 6.0.4 and also i tested on THIS live jira (i hope that i logged its version correctly)