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

src/share/vm/interpreter/interpreterRuntime.cpp

@@ -979,6 +979,7 @@ IRT_ENTRY(void, InterpreterRuntime::update_mdp_for_ret(JavaThread* thread, int r
   // ProfileData is essentially a wrapper around a derived oop, so we
   // need to take the lock before making any ProfileData structures.
   ProfileData* data = h_mdo->data_at(h_mdo->dp_to_di(fr.interpreter_frame_mdp()));
+  guarantee(data != NULL, "profile data must be valid");
   RetData* rdata = data->as_RetData();
   address new_mdp = rdata->fixup_ret(return_bci, h_mdo);
   fr.interpreter_frame_set_mdp(new_mdp);