Fix rocksdb_kv error process (#8744)

Signed-off-by: fishpenguin <kun.yu@zilliz.com>

internal/kv/rocksdb/rocksdb_kv.go

@@ -74,8 +74,11 @@ func (kv *RocksdbKV) Load(key string) (string, error) {
 	}
 
 	value, err := kv.DB.Get(kv.ReadOptions, []byte(key))
+	if err != nil {
+		return "", err
+	}
 	defer value.Free()
-	return string(value.Data()), err
+	return string(value.Data()), nil
 }
 
 // LoadWithPrefix returns a batch values of keys with a prefix
@@ -134,6 +137,7 @@ func (kv *RocksdbKV) MultiLoad(keys []string) ([]string, error) {
 		if err != nil {
 			return []string{}, err
 		}
+		defer value.Free()
 		values = append(values, string(value.Data()))
 		value.Free()
 	}

internal/kv/rocksdb/rocksdb_kv_test.go

@@ -174,4 +174,8 @@ func TestRocksdbKV_Dummy(t *testing.T) {
 	assert.Error(t, err)
 	err = rocksdbkv.DeleteRange("", "")
 	assert.Error(t, err)
+
+	rocksdbkv.ReadOptions = nil
+	_, err = rocksdbkv.Load("dummy")
+	assert.Error(t, err)
 }