Crosstab computeOffsets NullPointerException

[bence.gyongyossy]

I have a complex jrxml template (version 6.6.0) with a detail band containing several frames, one of which contains a list element which contains a crosstab element.
The height of the detail band changes dynamically depending on the data used to fill the template so it can appear on a page 1-3 times.

I believe in some cases it can't calculate where to place the crosstabs of the 2nd or 3rd detail band on the page because it would be out of the page and it gives an exception.
Here is the exception: 

java.lang.NullPointerException: null   at net.sf.jasperreports.engine.fill.JRFillCrosstab$CrosstabFiller.computeOffsets(JRFillCrosstab.java:1407) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFillCrosstab$CrosstabFiller.initCrosstab(JRFillCrosstab.java:1377) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFillCrosstab.rewind(JRFillCrosstab.java:1149) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFillElementContainer.rewind(JRFillElementContainer.java:1127) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.components.list.FillListContents.rewind(FillListContents.java:118) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.components.list.VerticalFillList.rewind(VerticalFillList.java:187) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFillComponentElement.rewind(JRFillComponentElement.java:225) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFillElementContainer.rewind(JRFillElementContainer.java:1127) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFillFrame.rewind(JRFillFrame.java:176) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFillElementContainer.rewind(JRFillElementContainer.java:1127) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFillBand.refill(JRFillBand.java:381) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:2642) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:813) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportContent(JRVerticalFiller.java:285) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:114) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:615) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.BaseReportFiller.fill(BaseReportFiller.java:413) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFiller.fill(JRFiller.java:120) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.fill.JRFiller.fill(JRFiller.java:103) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.JasperFillManager.fill(JasperFillManager.java:482) ~[jasperreports-6.6.0.jar:6.6.0]   at net.sf.jasperreports.engine.JasperFillManager.fill(JasperFillManager.java:443) ~[jasperreports-6.6.0.jar:6.6.0]   [/code]

I guess the problem is that because there can be several crosstabs in several list points it cannot tell in advance wheter a band will fit on a page or not.
The only way I could fully fix it is if I force it to put each detail band on its own page which is unacceptable for our client.
Any way I could make it so that if a band can't fit on a page because of the crosstabs it just places the band on the next page?