Bug 170763 Log files are created even if the log level has been set to OFF or the log dir to null
Even if you set the log level to OFF (e.g. within the BIRT report viewer web application) empty log files are created in BIRT's log directory. The same is the case if the log directory has been set to null. If the directory does not exist, a stack trace is printed to System.err. This is due to the fact that org.eclipse.birt.report.engine.api.impl.EngineLogger sets up a java.util.logging.FileHandler no matter what. It shouldn't do this if the log level is OFF or the directory is null.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/EngineLogger.java
logFileHandler = null;
	}
	/**
	 * Change the log level to the newLevel
	 * @param newLevel - new log level
	 */
	public static void changeLogLevel( Level newLevel )
	{
		Logger logger = Logger.getLogger( BIRT_NAME_SPACE );
		assert (logger != null);
		if ( newLevel != null )
		{
			if ( Level.OFF == logger.getLevel( ) && Level.OFF != newLevel )
			{
				createLogFile( logger );
			}
			logger.setLevel( newLevel );
		}
	}
	
	/**
	 * This is a utility function that will create an unique file name with the timestamp information in the file name and
	 * append the file name into the directory name.
	 * For example, if the directory name is C:\Log, the returned file name will be C:\Log\ReportEngine_2005_02_26_11_26_56.log.
	 * @param directoryName - the directory name of the log file. 
	 * @return An unique Log file name which is the directory name plus the file name.
	 */
	private static String generateUniqueLogFileName( String directoryName )
	{
		SimpleDateFormat df = new SimpleDateFormat("yyyy_MM_dd_HH_mm_ss");