Fixed an SVSNICK bug that could lead to duplicate users in very rare circumstances

Changes

@@ -3281,3 +3281,5 @@ This is the 3.2 fixes branch.
 - Fixed find_qline crashes regarding except tkl 'type qline', reported by Gilou (#0001882).
 - Fixed some CIDR bugs causing things not to match.
 - Fixed a CIDR bug when compiled without IPv6 support
+- Fixed an SVSNICK bug that could lead to duplicate users in very rare circumstances
+  (#0001874) reported by Jiuka.

src/modules/m_svsnick.c

@@ -97,14 +97,14 @@ int  m_svsnick(aClient *cptr, aClient *sptr, int parc, char *parv[])
         if (!hunt_server_token(cptr, sptr, MSG_SVSNICK, TOK_SVSNICK, "%s %s :%s", 1, parc,
 		parv) != HUNTED_ISME)
         {
+		if (do_nick_name(parv[2]) == 0)
+			return 0;
                 if ((acptr = find_person(parv[1], NULL)))
                 {
                         if (find_client(parv[2], NULL)) /* Collision */
                                 return exit_client(cptr, acptr, sptr,
                                     "Nickname collision due to Services enforced "
                                     "nickname change, your nick was overruled");
-                        if (do_nick_name(parv[2]) == 0)
-                                return 0;
                         acptr->umodes &= ~UMODE_REGNICK;
                         acptr->lastnick = TS2ts(parv[3]);
                         sendto_common_channels(acptr, ":%s NICK :%s", parv[1],