Bug 167511 [Block]NPE when using customized IStyleProcessor with Chart Generator and no Chart will be rendered
Use a customized IStyleProcessor with Generator.build() and the chart will not be rendered in UI.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/factory/Generator.java
elOrthogonalSeries = seOrthogonal.getDataDefinition( );
				if ( elOrthogonalSeries.isEmpty( ) )
				{
					throw new ChartException( ChartEnginePlugin.ID,
							ChartException.DATA_BINDING,
							"dataprocessor.exception.DefnExpMustAssociateY", 
							new Object[]{
									String.valueOf( iCount ), seOrthogonal
							},
							Messages.getResourceBundle( ) );
				}
				bAnyQueries = false;
				for ( int i = 0; i < elOrthogonalSeries.size( ); i++ )
				{
					qOrthogonalSeries = (Query) elOrthogonalSeries.get( i );
					if ( qOrthogonalSeries == null ) 
					{
						continue;
					}
					sExpression = qOrthogonalSeries.getDefinition( );
					if ( sExpression != null
							&& sExpression.trim( ).length( ) > 0 )
					{
						bAnyQueries = true;
						if ( !alExpressions.contains( sExpression ) )
						{
							alExpressions.add( sExpression ); 
						}
					}
				}