#fixed code
                                @SafeVarargs
    @SuppressWarnings("unchecked")
    public static <T> T[] mergeArrays(T[]... arrays) {
        if (isEmpty(arrays)) {
            throw new IllegalArgumentException("Merge arrays requires at least one array as argument");
        }

        return mergeArrays(length -> (T[]) Array.newInstance(arrays[0].getClass().getComponentType(), length), arrays);
    }
#vulnerable code 
                                @SafeVarargs
    @SuppressWarnings("unchecked")
    public static <T> T[] mergeArrays(T[]... arrays) {
        int size = 0;
        Class<?> type = null;

        for (T[] array : arrays) {
            size += array.length;
            type = array.getClass().getComponentType();
        }

        T[] mergedArray = (T[]) Array.newInstance(type, size);
        int index = 0;

        for (T[] array : arrays) {
            for (T element : array) {
                mergedArray[index++] = element;
            }
        }

        return mergedArray;
    } 
                            #location 12 
                            #vulnerability type NULL_DEREFERENCE