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
ReportDesignHandle handle = null;
		try
		{
			
			handle = sessionHandle.openDesign( reportConfigName );
			
			if ( handle != null )
			{
				Iterator parameters = parameterList.iterator( );
				while ( parameters != null && parameters.hasNext( ) )
				{
					Object parameterHandle = parameters.next( );
					if ( parameterHandle instanceof ScalarParameterHandle )
					{
						ScalarParameterHandle scalarParameterHandle = (ScalarParameterHandle) parameterHandle;
						if ( scalarParameterHandle.getName( ) != null )
							this.configMap.put(
									scalarParameterHandle.getName( ), null );
					}
				}
				Iterator configVars = handle.configVariablesIterator( );
				while ( configVars != null && configVars.hasNext( ) )
				{
					ConfigVariableHandle configVar = (ConfigVariableHandle) configVars
							.next( );
					if ( configVar != null && configVar.getName( ) != null )
					{
						
						String paramName = getParameterName( configVar
								.getName( ) );