I don't think there is a leak.

A little higher in the function, before all the conditions that you're
looking at, there is the statement
        s->stream_data.p = (void *) bzp;
so bzp is saved first and s->stream_data.p and bzp are actually the same
pointer.
I'm not sure why the assignment you're referring to since they are
already the same.  It could be historical, but I'd have to look at the logs.