Looks like it's having trouble loading the world, try using one of your backups. If you don't have any backups, it's a lot more complicated. Also, next time post this in the server tech support section
More specifically this is what probably happened.
// Don't be sad, have a hug! <3 -- (Smile
)
Description: Loading NBT data -- (The region files are saved as NBT data)
java.io.EOFException -- (End if file exception)
at java.io.DataInputStream.readByte(Unknown Source) -- (Unknown source because the file has ended and there's nowhere to read a byte from)
at net.minecraftforge.common.ForgeChunkManager.loadWorld(ForgeChunkManager.java:416) -- (It couldn't load all the data so it failed to load a chunk)