SV_USER: Fix /join allowing spectator to join without logging in

When sv_login set to 1, spectators do not need to login to connect,
but can then execute /join to convert to a player, skipping the
login process.

src/sv_user.c

@@ -2404,6 +2404,7 @@ Set client to player mode without reconnecting
 */
 static void Cmd_Join_f (void)
 {
+	extern cvar_t sv_login;
 	int i;
 	int clients;
 
@@ -2423,6 +2424,12 @@ static void Cmd_Join_f (void)
 		return;
 	}
 
+	// Might have been 'not necessary' for spectator but needed for player
+	if (sv_client->logged <= 0 && (int)sv_login.value) {
+		SV_ClientPrintf (sv_client, PRINT_HIGH, "This server requires users to login.  Please disconnect and reconnect as a player.\n");
+		return;
+	}
+
 	if (realtime - sv_client->connection_started < 5)
 	{
 		SV_ClientPrintf (sv_client, PRINT_HIGH, "Wait %d seconds\n", 5 - (int)(realtime - sv_client->connection_started));