Idiosyncrasies of Groovy's with method and null values

withNull.groovy

import org.codehaus.groovy.runtime.NullObject

def map = [ a: 1, b: 2 ]

// map.c is equal to null
assert map.c == null

// But then if we use with
map.c.with { c ->
    // c is not equal to null!
    assert c != null  

    // c is an instance of NullObject
    assert c instanceof NullObject

    // c is also equal to the singleton instance of NullObject
    assert c == NullObject.INSTANCE
    
    // But this is a MUCH neater way of checking
    assert c.is( null )
}

assert c != null sounds like a bug to me. Either null should always be a NullObject (which sounds like it's in the same realm as Scala's Optional), or it should be actually null. And for any cases where it cannot be one or the other, it should behave as if it is whichever one is "standard". (ie. NullObject == null)