Schould it be "null = null" oder something else?

[h-man2]

Currently, USE answers the question null = null with true

This can lead to situations that unintentionally supress errors in expressions.
For example, consider the following post-condition:

context List::insertAt(element:OclAny, index:Integer)
  post beforeAddedItem:
    self.elements@pre->subSequence(1, index-1) = self.elements->subSequence(1, index-1)

Evaluated on an empty list this evaluates to true, but this hides the erroneous access subSequence(1, 0) if called with insertAt('one', 1).

Any opinions on that?