[Bug]: [GOSDK] Expected to return nq ResultSet when searching from an empty collection

[ThreadDao]

Is there an existing issue for this?

• I have searched the existing issues

Environment

- Milvus version: master-20240617-e83ecd50-amd64
- Deployment mode(standalone or cluster):
- MQ type(rocksmq, pulsar or kafka):    
- SDK version(e.g. pymilvus v2.0.0rc2): go-sdk v2
- OS(Ubuntu or CentOS): 
- CPU/Memory: 
- GPU: 
- Others:

Current Behavior

Search func returns []ResultSet. When search from empty collection with 5(nq) vectors, the result is [], an empty slice.
Expected to return nq(5) ResultSet, though each ResultSet has 0 ResultCount, empty IDs, empty Scores, empty Fields, an Err search result is empty

type ResultSet struct {
	ResultCount  int // the returning entry count
	GroupByValue column.Column
	IDs          column.Column // auto generated id, can be mapped to the columns from `Insert` API
	Fields       DataSet       // output field data
	Scores       []float32     // distance to the target vector
	Err          error         // search error if any
}

Expected Behavior

No response

Steps To Reproduce

func TestSearchEmptySparseCollection(t *testing.T) {
	ctx := hp.CreateContext(t, time.Second*common.DefaultTimeout)
	mc := createDefaultMilvusClient(ctx, t)

	_, schema := hp.CollPrepare.CreateCollection(ctx, t, mc, hp.NewCreateCollectionParams(hp.Int64VarcharSparseVec), hp.TNewFieldsOption(),
		hp.TNewSchemaOption().TWithEnableDynamicField(true))
	hp.CollPrepare.CreateIndex(ctx, t, mc, hp.NewIndexParams(schema))
	hp.CollPrepare.Load(ctx, t, mc, hp.NewLoadParams(schema.CollectionName))

	// search
	vectors := hp.GenSearchVectors(common.DefaultNq, common.DefaultDim, entity.FieldTypeSparseVector)
	resSearch, errSearch := mc.Search(ctx, clientv2.NewSearchOption(schema.CollectionName, common.DefaultLimit, vectors).
		WithConsistencyLevel(entity.ClStrong).WithANNSField(common.DefaultSparseVecFieldName))
	common.CheckErr(t, errSearch, true)
	// common.CheckSearchResult(t, resSearch, 0, 0)
}

### Milvus Log

_No response_

### Anything else?

_No response_

[ThreadDao]

ref: https://github.com/milvus-io/milvus-sdk-go/pull/732/files#diff-60eded1585fa8112aac92a5d260eae8b0e4453f3aa501f29d32c237676107447

[congqixia]

/assign @ThreadDao

[ThreadDao]

fixed