fixed NPE when a chart has empty datasource and has custom series color map

git-svn-id: http://svn.code.sf.net/p/dynamicreports/code/trunk@779 bf0c503b-2351-4f66-9eae-aa52f3279a3f
added method setPrintWhenExpression to all report bands

git-svn-id: http://svn.code.sf.net/p/dynamicreports/code/trunk@780 bf0c503b-2351-4f66-9eae-aa52f3279a3f