log4j加载配置bug

异常信息：
log4j:ERROR setFile(null,true) call failed.
java.io.FileNotFoundException: 
	at java.io.FileOutputStream.open(Native Method)
	at java.io.FileOutputStream.<init>(FileOutputStream.java:221)
	at java.io.FileOutputStream.<init>(FileOutputStream.java:142)
	at org.apache.log4j.FileAppender.setFile(FileAppender.java:311)
	at org.apache.log4j.RollingFileAppender.setFile(RollingFileAppender.java:207)
	at org.apache.log4j.FileAppender.activateOptions(FileAppender.java:182)
	at org.apache.log4j.config.PropertySetter.activate(PropertySetter.java:307)
	at org.apache.log4j.config.PropertySetter.setProperties(PropertySetter.java:172)
	at org.apache.log4j.config.PropertySetter.setProperties(PropertySetter.java:104)
	at org.apache.log4j.PropertyConfigurator.parseAppender(PropertyConfigurator.java:842)
	at org.apache.log4j.PropertyConfigurator.parseCategory(PropertyConfigurator.java:768)
	at org.apache.log4j.PropertyConfigurator.configureRootCategory(PropertyConfigurator.java:648)
	at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:514)
	at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:580)
	at org.apache.log4j.helpers.OptionConverter.selectAndConfigure(OptionConverter.java:526)
	at org.apache.log4j.LogManager.<clinit>(LogManager.java:127)
	at org.apache.log4j.Logger.getLogger(Logger.java:117)
	at log4j.LogMoreFile.<clinit>(LogMoreFile.java:11)
经过查看源码，异常产生于：
  void setFile(String fileName, boolean append, boolean bufferedIO, int bufferSize)
                                                            throws IOException {
    LogLog.debug("setFile called: "+fileName+", "+append);

    // It does not make sense to have immediate flush and bufferedIO.
    if(bufferedIO) {
      setImmediateFlush(false);
    }

    reset();
    FileOutputStream ostream = null;
    try {
          //
          //   attempt to create file
          //
          ostream = new FileOutputStream(fileName, append);
    } catch(FileNotFoundException ex) {
          //
          //   if parent directory does not exist then
          //      attempt to create it and try to create file
          //      see bug 9150
          //
          String parentName = new File(fileName).getParent();
          if (parentName != null) {
             File parentDir = new File(parentName);
             if(!parentDir.exists() && parentDir.mkdirs()) {
                ostream = new FileOutputStream(fileName, append);
             } else {
                throw ex;
             }
          } else {
             throw ex;
          }
发现此处有个bug
经过查看官方：