Bug 145274 __isnull does not work properly when parameters have default value
steps to reproduce: - create a report - add a parameter with default value - preview report in web viewer - modify the url with __null pattern expected behavior: - __null takes effect actual behavior: - it simply didn't
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/context/ViewerAttributeBean.java
request, options );
		
		this.parameters = (HashMap) getParsedParameters(
				this.reportDesignHandle, parameterList, request, options );
		
		Collection parameterDefList = getReportService( )
				.getParameterDefinitions( this.reportDesignHandle, options,
						false );
		
		this.missingParameter = validateParameters( parameterDefList,
				this.parametersAsString );
	}
	/**
	 * parse paramenters from config file.
	 * 
	 * @param request
	 *            HttpServletRequest
	 * @return
	 */
	protected void parseConfigVars( HttpServletRequest request,
			Collection parameterList )
	{
		this.configMap = new HashMap( );
		
		String reportConfigName = ParameterAccessor
				.getConfigFileName( this.reportDesignName );
		if ( reportConfigName == null )
			return;
		
		SessionHandle sessionHandle = DesignEngine.newSession( ULocale.US );