Bug 137176 It takes unacceptable long time to render a report
Description: Get the attached report design, preview in report designer. It takes unacceptable long time to render a report, and users could not get the output finally. Even during the rending, the computer could not do anything else.
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/service/ReportEngineService.java
{
		assert task != null;
		assert parameters != null;
		boolean missingParameter = false;
		Collection parameterList = task.getParameterDefns( false );
		for ( Iterator iter = parameterList.iterator( ); iter.hasNext( ); )
		{
			IScalarParameterDefn parameterObj = (IScalarParameterDefn) iter
					.next( );
			
			
			
			String parameterName = parameterObj.getName( );
			Object parameterValue = parameters.get( parameterName );
			if ( parameterObj.isHidden( ) )
			{
				continue;
			}
			if ( parameterValue == null && !parameterObj.allowNull( ) )
			{
				missingParameter = true;
				break;
			}
			if ( IScalarParameterDefn.TYPE_STRING == parameterObj.getDataType( ) )
			{
				String parameterStringValue = (String) parameterValue;
				if ( parameterStringValue != null
						&& parameterStringValue.length( ) <= 0
						&& !parameterObj.allowBlank( ) )
				{