Fix check for whether we should write to prevent infinite loop

src/core/surface/call.c

@@ -445,17 +445,16 @@ static void finish_start_step(void *pc, grpc_op_error error) {
 static send_action choose_send_action(grpc_call *call) {
   switch (call->write_state) {
     case WRITE_STATE_INITIAL:
-      if (call->request_set[GRPC_IOREQ_SEND_INITIAL_METADATA] !=
-          REQSET_EMPTY) {
+      if (is_op_live(call, GRPC_IOREQ_SEND_INITIAL_METADATA)) {
         call->write_state = WRITE_STATE_STARTED;
         return SEND_INITIAL_METADATA;
       }
       return SEND_NOTHING;
     case WRITE_STATE_STARTED:
-      if (call->request_set[GRPC_IOREQ_SEND_MESSAGE] != REQSET_EMPTY) {
+      if (is_op_live(call, GRPC_IOREQ_SEND_MESSAGE)) {
         return SEND_MESSAGE;
       }
-      if (call->request_set[GRPC_IOREQ_SEND_CLOSE] != REQSET_EMPTY) {
+      if (is_op_live(call, GRPC_IOREQ_SEND_CLOSE)) {
         call->write_state = WRITE_STATE_WRITE_CLOSED;
         finish_ioreq_op(call, GRPC_IOREQ_SEND_TRAILING_METADATA, GRPC_OP_OK);
         finish_ioreq_op(call, GRPC_IOREQ_SEND_STATUS, GRPC_OP_OK);