ExecParams and ExecPrepared handle empty query

An empty query does not return CommandComplete. Instead it returns
EmptyQueryResponse.

pgconn.go

@@ -1406,6 +1406,8 @@ func (rr *ResultReader) receiveMessage() (msg pgproto3.BackendMessage, err error
 		rr.fieldDescriptions = msg.Fields
 	case *pgproto3.CommandComplete:
 		rr.concludeCommand(CommandTag(msg.CommandTag), nil)
+	case *pgproto3.EmptyQueryResponse:
+		rr.concludeCommand(nil, nil)
 	case *pgproto3.ErrorResponse:
 		rr.concludeCommand(nil, ErrorResponseToPgError(msg))
 	}

pgconn_test.go

@@ -668,6 +668,24 @@ func TestConnExecParamsPrecanceled(t *testing.T) {
 	ensureConnValid(t, pgConn)
 }
 
+func TestConnExecParamsEmptySQL(t *testing.T) {
+	t.Parallel()
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+	defer cancel()
+
+	pgConn, err := pgconn.Connect(ctx, os.Getenv("PGX_TEST_CONN_STRING"))
+	require.NoError(t, err)
+	defer closeConn(t, pgConn)
+
+	result := pgConn.ExecParams(ctx, "", nil, nil, nil, nil).Read()
+	assert.Nil(t, result.CommandTag)
+	assert.Len(t, result.Rows, 0)
+	assert.NoError(t, result.Err)
+
+	ensureConnValid(t, pgConn)
+}
+
 func TestConnExecPrepared(t *testing.T) {
 	t.Parallel()
 
@@ -797,6 +815,27 @@ func TestConnExecPreparedPrecanceled(t *testing.T) {
 	ensureConnValid(t, pgConn)
 }
 
+func TestConnExecPreparedEmptySQL(t *testing.T) {
+	t.Parallel()
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+	defer cancel()
+
+	pgConn, err := pgconn.Connect(ctx, os.Getenv("PGX_TEST_CONN_STRING"))
+	require.NoError(t, err)
+	defer closeConn(t, pgConn)
+
+	_, err = pgConn.Prepare(ctx, "ps1", "", nil)
+	require.NoError(t, err)
+
+	result := pgConn.ExecPrepared(ctx, "ps1", nil, nil, nil).Read()
+	assert.Nil(t, result.CommandTag)
+	assert.Len(t, result.Rows, 0)
+	assert.NoError(t, result.Err)
+
+	ensureConnValid(t, pgConn)
+}
+
 func TestConnExecBatch(t *testing.T) {
 	t.Parallel()