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
if ( !bAnyQueries )
				{
					throw new ChartException( ChartEnginePlugin.ID,
							ChartException.DATA_BINDING,
							"dataprocessor.exception.AtLeastOneDefnExpMustAssociateY", 
							new Object[]{
									String.valueOf( iCount ), seOrthogonal
							},
							Messages.getResourceBundle( ) );
				}
				
				String[] triggerExprs = DataProcessor.getSeriesTriggerExpressions( seOrthogonal,
						iae );
				if ( triggerExprs != null )
				{
					for ( int t = 0; t < triggerExprs.length; t++ )
					{
						String tgexp = triggerExprs[t];
						if ( !alExpressions.contains( tgexp ) )
						{
							alExpressions.add( tgexp ); 
						}
					}
				}
			}
		}
		return alExpressions;
	}
}