Fixed an annoying message that was happening with botclients from mods spamming too much stuff at once.

git-svn-id: https://svn.code.sf.net/p/fteqw/code/trunk@1330 fc73d0e0-1445-4013-8a0c-d673dee63da5

engine/server/sv_send.c

@@ -1816,6 +1816,7 @@ void SV_SendClientMessages (void)
 		{
 			SZ_Clear (&c->netchan.message);
 			SZ_Clear (&c->datagram);
+			c->num_backbuf = 0;
 			continue;
 		}