#vulnerable code 
                             private static String getRefValue(Properties result, String v) {
		if (v != null) {
			while (v.startsWith(REF)) {
				String ref = v.substring(1);
				v = result.getProperty(ref);
				if (v == null) {
					v = System.getProperty(ref);
				}
			}
		}
		return v == null ? "" : v;
	} 
                            #location 3 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             private static String getRefValue(Properties result, String v) {
		while (v != null && v.startsWith(REF)) {
			String ref = v.substring(1);
			v = result.getProperty(ref);
			if (v == null) {
				v = System.getProperty(ref);
			}
		}
		return v == null ? "" : v;
	}