add explicit error for null hostToken

Author: Lavodan

src/client/HostLobbyModal.ts

@@ -592,6 +592,9 @@ export class HostLobbyModal extends LitElement {
 
     createLobby(this.lobbyCreatorClientID)
       .then((lobby) => {
+		if (lobby.hostToken === null) {
+			throw new Error("Server did not return hostToken for private lobby");
+		}
         this.lobbyId = lobby.gameInfo.gameID;
         // join lobby
         const cookieDurationSec = 60 * 60 * 6; // store for max 6 hours