Freeze when quitting a level while the /locate command is busy searching

Expected:
Return to the main menu as usual.

Instead:
Game freezes, never recovers, never crashes.

Steps to reproduce:

1. Make a Customized world with just a Savannah biome

2. /locate Mansion (it will take some time before concluding there is no Mansion)

3. Immediately, while /locate is still busy, hit "Save and Quit to Title".

4. Game freezes. Never throws anything or crashes or quits back to the launcher. Just freezes.

Game output:

• At 11:55:53 I hit ESC, and it saves the level

• At 11:56:09, it disconnects player, stops server and saves the level, as usual

• It never gets to the "Stopping!" or "SoundSystem shutting down..." messages.

Completely ignored arguments: [--nativeLauncherVersion, 307]
[11:55:45] [Client thread/INFO]: Setting user: sealbudsman
[11:55:45] [Client thread/WARN]: Skipping bad option: lastServer:
[11:55:45] [Client thread/INFO]: LWJGL Version: 2.9.4
[11:55:46] [Client thread/INFO]: Reloading ResourceManager: Default
[11:55:46] [Sound Library Loader/INFO]: Starting up SoundSystem...
[11:55:46] [Thread-5/INFO]: Initializing LWJGL OpenAL
[11:55:46] [Thread-5/INFO]: (The LWJGL binding of OpenAL.  For more information, see http://www.lwjgl.org)
AL lib: (EE) MMDevApiOpenPlayback: Device init failed: 0x80070490
AL lib: (EE) MMDevApiOpenPlayback: Device init failed: 0x80070490
[11:55:46] [Thread-5/ERROR]: Error in class 'LibraryLWJGLOpenAL'
[11:55:46] [Thread-5/ERROR]: Unable to initialize OpenAL.  Probable cause: OpenAL not supported.
[11:55:46] [Thread-5/WARN]: ERROR MESSAGE:
[11:55:46] [Thread-5/INFO]: Could not locate OpenAL library.
[11:55:46] [Thread-5/WARN]: STACK TRACE:
[11:55:46] [Thread-5/INFO]: org.lwjgl.openal.AL.create(AL.java:156)
[11:55:46] [Thread-5/INFO]: org.lwjgl.openal.AL.create(AL.java:102)
[11:55:46] [Thread-5/INFO]: org.lwjgl.openal.AL.create(AL.java:206)
[11:55:46] [Thread-5/INFO]: paulscode.sound.libraries.LibraryLWJGLOpenAL.init(LibraryLWJGLOpenAL.java:164)
[11:55:46] [Thread-5/INFO]: paulscode.sound.SoundSystem.CommandNewLibrary(SoundSystem.java:1576)
[11:55:46] [Thread-5/INFO]: paulscode.sound.SoundSystem.CommandQueue(SoundSystem.java:2572)
[11:55:46] [Thread-5/INFO]: paulscode.sound.CommandThread.run(CommandThread.java:121)
[11:55:46] [Sound Library Loader/WARN]: ERROR MESSAGE:
[11:55:46] [Sound Library Loader/INFO]: Could not locate OpenAL library.
[11:55:46] [Sound Library Loader/INFO]: Starting up SoundSystem...
[11:55:47] [Thread-7/INFO]: Switching to No Sound
[11:55:47] [Thread-7/INFO]: (Silent Mode)
[11:55:47] [Sound Library Loader/INFO]: Sound engine started
[11:55:48] [Client thread/INFO]: Created: 1024x512 textures-atlas
[11:55:51] [Server thread/INFO]: Starting integrated minecraft server version 16w43a
[11:55:51] [Server thread/INFO]: Generating keypair
[11:55:51] [Server thread/INFO]: Preparing start region for level 0
[11:55:52] [Server thread/INFO]: Changing view distance to 12, from 10
[11:55:53] [Server thread/INFO]: sealbudsman[local:E:e12d7e01] logged in with entity id 133 at (-43.49945781345387, 82.0063695184198, 32.7650408073702)
[11:55:53] [Server thread/INFO]: sealbudsman joined the game
[11:55:53] [Server thread/INFO]: Saving and pausing game...
[11:55:53] [Server thread/INFO]: Saving chunks for level 'SAVANNA'/Overworld
[11:55:53] [Server thread/INFO]: Saving chunks for level 'SAVANNA'/Nether
[11:55:53] [Server thread/INFO]: Saving chunks for level 'SAVANNA'/The End
[11:56:09] [Server thread/INFO]: sealbudsman lost connection: TextComponent{text='Disconnected', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
[11:56:09] [Server thread/INFO]: sealbudsman left the game
[11:56:09] [Server thread/INFO]: Stopping singleplayer server as player logged out
[11:56:09] [Server thread/INFO]: Stopping server
[11:56:09] [Server thread/INFO]: Saving players
[11:56:09] [Server thread/INFO]: Saving worlds
[11:56:09] [Server thread/INFO]: Saving chunks for level 'SAVANNA'/Overworld
[11:56:09] [Server thread/INFO]: Saving chunks for level 'SAVANNA'/Nether
[11:56:09] [Server thread/INFO]: Saving chunks for level 'SAVANNA'/The End