8184009: Missing null pointer check in InterpreterRuntime::update_mdp_for_ret() Summary: Adds a missing null check (guarantee) found by Parfait. Reviewed-by: coleenp, shade

^build/
^dist/
^.idea/
nbproject/private/
^webrev
^.src-rev$
^.jib/
.DS_Store
.metadata/
.recommenders/