Bukkit

What steps will reproduce the problem?
1. Use Spigot 1.9 and multiworld 5.2.7
2. Have an already loaded flatland world
3. Have a player move to an area not already generated

What is the expected output? What do you see instead?
Expected output is the generation of new chunks. Instead see a server crash with the following error.

[10:52:49 INFO]: jamescowens[jco-linux.jcowens.net/192.168.0.6:56126] logged in with entity id 10172 at ([Big_project_World]-1873.3010138895095, 183.4004001862646, -2507.97699037607)
[10:52:50 ERROR]: Encountered an unexpected exception
java.lang.NoSuchFieldError: MUSHROOM_SHORE
        at multiworld.worldgen.populators.MyceliumPopulator.chanceBlock(MyceliumPopulator.java:22) ~[?:?]
        at multiworld.worldgen.populators.SurfacePopulator.populate(SurfacePopulator.java:28) ~[?:?]
        at net.minecraft.server.v1_9_R1.Chunk.a(Chunk.java:945) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at net.minecraft.server.v1_9_R1.Chunk.loadNearby(Chunk.java:909) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at org.bukkit.craftbukkit.v1_9_R1.chunkio.ChunkIOProvider.callStage2(ChunkIOProvider.java:73) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at org.bukkit.craftbukkit.v1_9_R1.chunkio.ChunkIOProvider.callStage2(ChunkIOProvider.java:1) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at org.bukkit.craftbukkit.v1_9_R1.util.AsynchronousExecutor$Task.finish(AsynchronousExecutor.java:188) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at org.bukkit.craftbukkit.v1_9_R1.util.AsynchronousExecutor.finishActive(AsynchronousExecutor.java:347) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at org.bukkit.craftbukkit.v1_9_R1.chunkio.ChunkIOExecutor.tick(ChunkIOExecutor.java:34) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at net.minecraft.server.v1_9_R1.MinecraftServer.D(MinecraftServer.java:740) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at net.minecraft.server.v1_9_R1.DedicatedServer.D(DedicatedServer.java:400) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at net.minecraft.server.v1_9_R1.MinecraftServer.C(MinecraftServer.java:660) ~[spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:559) [spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e]
        at java.lang.Thread.run(Thread.java:745) [?:1.8.0_72]
[10:52:50 ERROR]: This crash report has been saved to: /home/minecraft/minecraft_server/./crash-reports/crash-2016-03-06_10.52.50-server.txt
[10:52:50 INFO]: Stopping server

What version of the product are you using?

The latest multiworld (5.2.7)

What version of the craftbukkit/bukkit are you using?

The latest Spigot 1.9 (spigot-1.9-R0.1-SNAPSHOT-20160306093504.jar:git-Spigot-bc01c3a-935349e)

Do you have an error log of what happened?

See above, also see the attached crash report...

Please provide the result of /mw debug below:

[11:17:50 INFO]: [MultiWorld] Now printing debug information
[11:17:50 INFO]: [MultiWorld] MultiWorld version: 5.2.7
[11:17:50 INFO]: [MultiWorld] Bukkit version: git-Spigot-bc01c3a-935349e (MC: 1.9)
[11:17:50 INFO]: [MultiWorld]
[11:17:50 INFO]: [MultiWorld] --<[Modules]>--
[11:17:50 INFO]: [MultiWorld] [State, pluginName]
[11:17:50 INFO]: [MultiWorld] [Working, EndPortalHandler]
[11:17:50 INFO]: [MultiWorld] [Unloaded, EnderChestBlokker]
[11:17:50 INFO]: [MultiWorld] [Unloaded, WorldChatSeperatorPlugin]
[11:17:50 INFO]: [MultiWorld] [Unloaded, GameModeChancer]
[11:17:50 INFO]: [MultiWorld] [Unloaded, WorldSpawnHandler]
[11:17:50 INFO]: [MultiWorld] [Working, NetherPortalHandler]
[11:17:50 INFO]: [MultiWorld]
[11:17:50 INFO]: [MultiWorld] --<[CommandStacks]>--
[11:17:50 INFO]: [MultiWorld] multiworld.command.DefaultCommandStack
[11:17:50 INFO]: [MultiWorld]  - /mw []
[11:17:50 INFO]: [MultiWorld] multiworld.command.DefaultCommandStack
[11:17:50 INFO]: [MultiWorld]  - /mw [debug]

I fixed this myself. Fortunately the newest multiworld has the source included. I pulled it into Eclipse and edited line 22 of the MyceliumPopulator.java file to remove the reference to MUSHROOM_SHORE, which is apparently an element that does not exist. Line 22 now reads...

if (block.getBiome() == Biome.MUSHROOM_ISLAND)

(The "or" condition and the second constant MUSHROOM_SHORE I removed.)

I recompiled and re-exported the multiworld jar and everything appears to work fine now.