Category series name is null

[erickentry]

I tried to build a report containing a line chart, following this example:

http://dynamicjasper.com/docs/current/xref-test/ar/com/fdvs/dj/test/domain/chart/builder/LineChartBuilderTest.html

But I got this error instead:

Category series name is null.
net.sf.jasperreports.engine.JRRuntimeException: Category series name is null.
	at net.sf.jasperreports.charts.fill.JRFillCategoryDataset.customIncrement(JRFillCategoryDataset.java:134)
	at net.sf.jasperreports.engine.fill.JRFillElementDataset.increment(JRFillElementDataset.java:211)
	at net.sf.jasperreports.engine.fill.JRCalculator.incrementDataset(JRCalculator.java:486)
	at net.sf.jasperreports.engine.fill.JRCalculator.initializeVariables(JRCalculator.java:363)
	at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportContent(JRVerticalFiller.java:291)
	at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:123)
	at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:622)
	at net.sf.jasperreports.engine.fill.BaseReportFiller.fill(BaseReportFiller.java:433)
	at net.sf.jasperreports.engine.fill.JRFiller.fill(JRFiller.java:162)
	at net.sf.jasperreports.engine.fill.JRFiller.fill(JRFiller.java:145)
	at net.sf.jasperreports.engine.JasperFillManager.fill(JasperFillManager.java:758)
	at net.sf.jasperreports.engine.JasperFillManager.fillToStream(JasperFillManager.java:716)
	at net.sf.jasperreports.engine.JasperFillManager.fillToStream(JasperFillManager.java:696)
	at net.sf.jasperreports.engine.JasperFillManager.fillReportToStream(JasperFillManager.java:1034)

I've been dealing with this for three days, but I haven't found any workaround anywhere...

My dependencies:

'net.sf.jasperreports:jasperreports:6.17.0'
'com.lowagie:itext:2.1.7.js8'
'ar.com.fdvs:DynamicJasper:5.3.2'