fix: slapd with rwm overlay segfault following ldapmodify

(newSup is NULL if it was specified, but same as old Sup)

Author: Howard Chu <hyc@openldap.org>
Upstream ITS: #7414
Upstream commit: d42c7c4
Resolves: #865685

diff --git a/servers/slapd/overlays/rwm.c b/servers/slapd/overlays/rwm.c
index cc6211e..d12fd0f 100644
--- a/servers/slapd/overlays/rwm.c
+++ b/servers/slapd/overlays/rwm.c
@@ -107,10 +107,12 @@ rwm_op_rollback( Operation *op, SlapReply *rs, rwm_op_state *ros )
 		break;
 	case LDAP_REQ_MODRDN:
 		if ( op->orr_newSup != ros->orr_newSup ) {
-			ch_free( op->orr_newSup->bv_val );
-			ch_free( op->orr_nnewSup->bv_val );
-			op->o_tmpfree( op->orr_newSup, op->o_tmpmemctx );
-			op->o_tmpfree( op->orr_nnewSup, op->o_tmpmemctx );
+			if ( op->orr_newSup ) {
+				ch_free( op->orr_newSup->bv_val );
+				ch_free( op->orr_nnewSup->bv_val );
+				op->o_tmpfree( op->orr_newSup, op->o_tmpmemctx );
+				op->o_tmpfree( op->orr_nnewSup, op->o_tmpmemctx );
+			}
 			op->orr_newSup = ros->orr_newSup;
 			op->orr_nnewSup = ros->orr_nnewSup;
 		}
-- 
1.7.11.7