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
* @param configVarName
	 *            String
	 * @return String
	 */
	private String getParameterName( String configVarName )
			throws ReportServiceException
	{
		String paramName = null;
		
		List parameters = getParameterList( );
		if ( parameters != null )
		{
			for ( int i = 0; i < parameters.size( ); i++ )
			{
				ScalarParameterHandle parameter = null;
				if ( parameters.get( i ) instanceof ScalarParameterHandle )
				{
					parameter = ( (ScalarParameterHandle) parameters.get( i ) );
				}
				
				String curName = null;
				if ( parameter != null && parameter.getName( ) != null )
				{
					curName = parameter.getName( ) + "_" + parameter.getID( ); 
				}
				
				if ( curName != null
						&& curName.equalsIgnoreCase( configVarName ) )
				{
					paramName = parameter.getName( );