Don't try to signal an empty semaphore path if the netmail_sem is blank.

src/sbbs3/postmsg.cpp

@@ -462,7 +462,7 @@ extern "C" int DLLCALL savemsg(scfg_t* cfg, smb_t* smb, smbmsg_t* msg, client_t*
 	if((i=smb_addmsg(smb,msg,smb_storage_mode(cfg, smb),dupechk_hashes,xlat,(uchar*)msgbuf, /* tail: */NULL))==SMB_SUCCESS
 		&& msg->to!=NULL	/* no recipient means no header created at this stage */) {
 		if(smb->subnum == INVALID_SUB) {
-			if(msg->to_net.type == NET_FIDO)
+			if(msg->to_net.type == NET_FIDO && cfg->netmail_sem[0])
 				ftouch(cmdstr(cfg,NULL,cfg->netmail_sem,nulstr,nulstr,NULL));
 		} else
 			signal_sub_sem(cfg,smb->subnum);