use ?.<operator> to fix the problem

MutablePropertyCouldHaveChanged4.kt

    /**
     * use "?.let" to create a lambda in which we're sure there's no problem.
     * Is a very nice solution, if possible.
     */
    @Test
    fun mutablePropertyCouldHaveChanged4() {
        name?.let { assertThat(it.length).isNotZero() }
    }