VectorUtils#vector result is null ,leading to NPE

[yeyinglang]

question:

We use the Search API to execute queries based on scalar filter conditions. （notes: in this case,we should use query API）
Then VectorUtils#ConvertToGrpcSearchRequest will throw NPE

io.milvus.v2.utils.VectorUtils#ConvertToGrpcSearchRequest

Reproduction Code

            SearchReq searchReq = SearchReq.builder()
                    .collectionName(Constant.COLLECTION_NAME)
                    .filter("id ==4627727850274838")
                    .outputFields(Arrays.asList("text", "id"))
                    .limit(1)
                    .build();

            SearchResp searchResp = milvusClient.search(searchReq);

[yhmo]

The fix pr is mergerd.