Fix #4833

deleting the synced projectile was originally based on when there are no
more unsynced subparticles, which led to desyncs if they weren't created
due to hitting the limit
This was changed to deleting the projectile after ttl+ParticleTTL

rts/Sim/Projectiles/FireProjectile.cpp

@@ -138,9 +138,7 @@ void CFireProjectile::Update()
 		pi->posDif*=0.9f;
 	}
 
-	if (subParticles.empty() && (ttl <= 0)) {
-		deleteMe = true;
-	}
+	deleteMe |= ttl <= -particleTime;
 }
 
 void CFireProjectile::Draw()