#vulnerable code 
                                protected void prepareConfigOutputFolder() {
	File f = new File(evoConfig.getOutputFolder() + this.getConfig().getOutputFolder());
	if (evoConfig.isCleanStart()) {
	    if (f.exists()) {
		for (File tempFile : f.listFiles()) {
		    tempFile.delete();
		}
	    }
	}
	f.mkdirs();
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                protected void prepareConfigOutputFolder() {
	ruleFolder = new File(evoConfig.getOutputFolder() + this.getConfig().getOutputFolder());
	if (evoConfig.isCleanStart()) {
	    if (ruleFolder.exists()) {
		for (File tempFile : ruleFolder.listFiles()) {
		    tempFile.delete();
		}
	    }
	}
	ruleFolder.mkdirs();
    }