services/identity/internal/revocation: Avoid nil ptr dereference

Change-Id: Id74e12abb3bd0d8e6066853feaf4d88786e726bd
diff --git a/services/identity/internal/revocation/sql_database.go b/services/identity/internal/revocation/sql_database.go
index b50beb5..e5f57aa 100644
--- a/services/identity/internal/revocation/sql_database.go
+++ b/services/identity/internal/revocation/sql_database.go
@@ -38,10 +38,10 @@
 
 func (s *sqlDatabase) IsRevoked(revocationCaveatID []byte) (bool, error) {
 	rows, err := s.isRevokedStmt.Query(hex.EncodeToString(revocationCaveatID))
-	defer rows.Close()
 	if err != nil {
 		return false, err
 	}
+	defer rows.Close()
 	return rows.Next(), err
 }