Empty RegionAction added to MultiRequest in case of RowMutations/CheckAndMutate batch

When a client sends RowMutations/CheckAndMutate batch requests, no Action objects are added to the builder (RegionAction.Builder), so empty RegionAction is added to MultiRequest at the following line:
https://github.com/apache/hbase/blob/3c319811799cb4c1f51fb5b43dd4743acd28052c/hbase-client/src/main/java/org/apache/hadoop/hbase/shaded/protobuf/RequestConverter.java#L593

We need to check if the builder has any Action objects or not here.