AssertionError when replacing missing key

[fvlad]

Hi. I'm using jctools 2.1.2.
I found that when I try to replace a value in NBHM for a key that doesn't exit, I get AssertionError. Here is the sample test:

@Test
public void replaceTest() {
    final ConcurrentMap<String, String> map = new NonBlockingHashMap<>();

    assertNull(map.replace(UUID.randomUUID().toString(), UUID.randomUUID().toString()));
    assertFalse(map.replace(UUID.randomUUID().toString(), UUID.randomUUID().toString(), UUID.randomUUID().toString()));
}

The test works fine when I replace NBHM with ConcurrentHashMap.