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 ( externalContext != null
				&& externalContext.getScriptable( ) != null )
		{
			sh.init( externalContext.getScriptable( ) );
		}
		else
		{
			sh.init( null );
		}
		sh.setRunTimeModel( cmRunTime );
		final String sScriptContent = cmRunTime.getScript( );
		if ( sScriptContent != null )
		{
			sh.register( sScriptContent );
		}
		
		
		/*
		 * ScriptHandler.callFunction( sh, ScriptHandler.ON_PREPARE, cmRunTime,
		 * rtc.getScriptContext( ) );
		 */
		return rtc;
	}
	/**
	 * Builds and computes preferred sizes of various chart components offscreen
	 * using the provided display server.
	 * 
	 * @param ids
	 *            A display server using which the chart may be built.