- Critical crash fix. Please update your servers.

git-svn-id: https://svn.code.sf.net/p/rathena/svn/trunk@13678 54d463be-8e91-2dee-dedb-b68131a5f0ec

src/map/clif.c

@@ -9796,6 +9796,9 @@ void clif_parse_NpcStringInput(int fd, struct map_session_data* sd)
 	int message_len = RFIFOW(fd,2)-8;
 	int npcid = RFIFOL(fd,4);
 	const char* message = (char*)RFIFOP(fd,8);
+	
+	if( message_len < 0 )
+		message_len = 0;
 
 	safestrncpy(sd->npc_str, message, min(message_len,CHATBOX_SIZE));
 	npc_scriptcont(sd, npcid);