since

commit 4bcf1872
Date:   Thu Oct 13 23:43:41 2016 +0200

    chartx: fix sparse chart import

because

- Matrix< Any > aMatrix( rDataSeq.maData.size(), 1 );
+ Matrix< Any > aMatrix( rDataSeq.mnPointCount, 1 );

where rDataSeq.mnPointCount is -1

Change-Id: I4bb4805dd81a342d4c0ce24e3240154daf53b452