Suspicious code in GraphKit::record_profiled_receiver_for_speculation

[Roland Westrelin]

> Thanks for reporting this issue! The "return n" was introduced by JDK-8031755 [1] and I think it can be removed. I filed JDK-8160942 [2] to investigate.

As Radek pointed it's not only the extra return, it's also the
assignment to maybe_null in the if that has no effect because a second
maybe_null is declared there.

Roland.