A builder on our server filled sand with (Async)WorldEdit in the air, and after a short time the server randomly crashed. This happend two times in a row with the same error.

[14:33:43] [Server thread/INFO]: JoJoYoshy issued server command: //set 12
[14:33:43] [Server thread/INFO]: WorldEdit: JoJoYoshy (in "city_hub"): /set 12 - Region: (-3738.0, 42.0, 4096.0) - (-3278.0, 50.0, 4098.0)
[14:33:47] [Server thread/ERROR]: Encountered an unexpected exception
net.minecraft.server.v1_8_R3.ReportedException: Exception ticking world
at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:781) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot.jar:git-Spigot-db6de12-18fbb24]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_40]
Caused by: java.util.NoSuchElementException
at java.util.TreeMap.key(TreeMap.java:1323) ~[?:1.8.0_40]
at java.util.TreeMap.firstKey(TreeMap.java:290) ~[?:1.8.0_40]
at java.util.TreeSet.first(TreeSet.java:394) ~[?:1.8.0_40]
at org.bukkit.craftbukkit.v1_8_R3.util.HashTreeSet.first(HashTreeSet.java:114) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.WorldServer.a(WorldServer.java:629) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.WorldServer.doTick(WorldServer.java:249) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:770) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
... 4 more
[14:33:47] [Server thread/ERROR]: Cause of unexpected exception was
java.util.NoSuchElementException
at java.util.TreeMap.key(TreeMap.java:1323) ~[?:1.8.0_40]
at java.util.TreeMap.firstKey(TreeMap.java:290) ~[?:1.8.0_40]
at java.util.TreeSet.first(TreeSet.java:394) ~[?:1.8.0_40]
at org.bukkit.craftbukkit.v1_8_R3.util.HashTreeSet.first(HashTreeSet.java:114) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.WorldServer.a(WorldServer.java:629) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.WorldServer.doTick(WorldServer.java:249) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:770) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot.jar:git-Spigot-db6de12-18fbb24]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_40]
[14:33:47] [Server thread/ERROR]: This crash report has been saved to: /./crash-reports/crash-2015-12-12_14.33.47-server.txt
[14:33:47] [Server thread/INFO]: Stopping server