Disconnect client if using an invalid Mojang account (#975)

This commit supresses the NPE that was previously sent when using an invalid Mojang account. Instead, the Bedrock client is disconnected with an error message.

connector/src/main/java/org/geysermc/connector/network/session/GeyserSession.java

@@ -350,6 +350,11 @@ public class GeyserSession implements CommandSender {
                     public void connected(ConnectedEvent event) {
                         loggingIn = false;
                         loggedIn = true;
+                        if (protocol.getProfile() == null) {
+                            // Java account is offline
+                            disconnect(LanguageUtils.getPlayerLocaleString("geyser.network.remote.invalid_account", clientData.getLanguageCode()));
+                            return;
+                        }
                         connector.getLogger().info(LanguageUtils.getLocaleStringLog("geyser.network.remote.connect", authData.getName(), protocol.getProfile().getName(), remoteServer.getAddress()));
                         playerEntity.setUuid(protocol.getProfile().getId());
                         playerEntity.setUsername(protocol.getProfile().getName());