Bug 147407 Preview the attached report in the web viewer first time and then click the TOC button will cause NPE error
Description: It just can be reprouduced at first time preview. Step to reproduce: 1. please use attach report file 2. preview it in the web viewer 3. click the "Toggle table of contents" button Actual result: As the atteched screenshot shows,There is a NPE error.And if you preview it in the Web viewer again, the phenomenon is disappear.But reopen the eclipse and preview it at first time, it will be occured.
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/utility/ParameterAccessor.java
* 
	 * @param config
	 *            Servlet configuration
	 */
	public synchronized static void initParameters( ServletConfig config )
	{
		
		ServletContext context = config.getServletContext( );
		workingFolder = context.getInitParameter( INIT_PARAM_REPORT_DIR );
		if ( workingFolder == null || workingFolder.trim( ).length( ) <= 0 )
		{
			
			workingFolder = context.getRealPath( "/" ); 
		}
		
		
		if ( workingFolder != null
				&& workingFolder.trim( ).endsWith( File.separator ) )
		{
			workingFolder = workingFolder.trim( ).substring( 0,
					workingFolder.trim( ).length( ) - 1 );
		}
		
		webAppLocale = getLocaleFromString( context
				.getInitParameter( INIT_PARAM_LOCALE ) );
		if ( webAppLocale == null )
			webAppLocale = Locale.getDefault( );
		isWorkingFolderAccessOnly = Boolean
				.valueOf(
						context