[MC-78481] Realms: "World is closed" shows as "mco.errorMessage.403"

A closed realm shows it's error message as mco.errorMessage.403 instead of human readable text.

Logfile shows plain text:

[20:59:25] [Client thread/INFO]: Realms library version == 1.7.12
[20:59:26] [MCO Availability Checker #1/INFO]: Realms is available for this user
[20:59:29] [Realms-long-running-task/ERROR]: Couldn't connect to world
com.mojang.realmsclient.exception.RealmsServiceException: {"errorCode":403, "errorMsg":"World is closed"}
	at com.mojang.realmsclient.client.RealmsClient.execute(RealmsClient.java:394) ~[realms-1.7.12.jar:1.7.12]
	at com.mojang.realmsclient.client.RealmsClient.join(RealmsClient.java:116) ~[realms-1.7.12.jar:1.7.12]
	at com.mojang.realmsclient.gui.RealmsConnectTask.run(RealmsConnectTask.java:44) [realms-1.7.12.jar:1.7.12]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_25]

Happened after restoring a backup. Server had closed "itself".
Restarting Minecraft didn't change anything.