filter('v:_null_list, 'v:val') should return v:_null_list and a similar
statement should hold for map.
Changes after review
* Test inserted in legacy test suite has been removed by reverting the commit
adding it.
* Change the fix to tv_copy the argument before returning.
* Readd the two tests on crashes, and modified their expected return value.
* Move the test from 'incorrect behaviour' section to 'correct behaviour section'
* Add analogous tests for v:_null_dict
Always copy list or dictionary to return variable
If the type of input is correct (i.e. either a list or a dictionary), this
should also be returned.
d763d2fe7a