Summary: After exiting a singleplayer world, there is brief lag, then the world exits to the title screen. During the brief lag, an Invalid Session id error appears on the launcher, apparently, the user is being authorized by a Realms Server, though the Minecraft Realms was never clicked.

Game Output: (Truncated to section with 'Invalid Session id' error):
[19:26:25] [pool-4-thread-3/INFO]: Could not authorize you against Realms server: Invalid session id
[19:26:25] [pool-4-thread-1/INFO]: Could not authorize you against Realms server: Invalid session id
[19:26:25] [pool-4-thread-3/ERROR]: Couldn't get pending invite count
com.mojang.realmsclient.exception.RealmsServiceException: Invalid session id
at com.mojang.realmsclient.client.RealmsClient.execute(RealmsClient.java:394) ~[realms-1.7.59.jar:1.7.59]
at com.mojang.realmsclient.client.RealmsClient.pendingInvitesCount(RealmsClient.java:285) ~[realms-1.7.59.jar:1.7.59]
at com.mojang.realmsclient.gui.RealmsDataFetcher$PendingInviteUpdateTask.updatePendingInvites(RealmsDataFetcher.java:236) [realms-1.7.59.jar:1.7.59]
at com.mojang.realmsclient.gui.RealmsDataFetcher$PendingInviteUpdateTask.run(RealmsDataFetcher.java:227) [realms-1.7.59.jar:1.7.59]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.FutureTask.runAndReset(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.7.0_71]
at java.lang.Thread.run(Unknown Source) [?:1.7.0_71]
[19:26:25] [pool-4-thread-1/ERROR]: Couldn't get trial availability
com.mojang.realmsclient.exception.RealmsServiceException: Invalid session id
at com.mojang.realmsclient.client.RealmsClient.execute(RealmsClient.java:394) ~[realms-1.7.59.jar:1.7.59]
at com.mojang.realmsclient.client.RealmsClient.trialAvailable(RealmsClient.java:339) ~[realms-1.7.59.jar:1.7.59]
at com.mojang.realmsclient.gui.RealmsDataFetcher$TrialAvailabilityTask.getTrialAvailable(RealmsDataFetcher.java:263) [realms-1.7.59.jar:1.7.59]
at com.mojang.realmsclient.gui.RealmsDataFetcher$TrialAvailabilityTask.run(RealmsDataFetcher.java:254) [realms-1.7.59.jar:1.7.59]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.FutureTask.runAndReset(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.7.0_71]
at java.lang.Thread.run(Unknown Source) [?:1.7.0_71]
[19:26:27] [Client thread/INFO]: Stopping!
[19:26:27] [Client thread/INFO]: SoundSystem shutting down...
[19:26:27] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com