Exception Ticking World Server Crash

I'm not an expert on crash reports but this might mean something:

Is Modded: Unknown (can't tell)

(found on last line of both reports)

I don't know what that means. I've never dealt with Vanilla crash reports.
I can tell you that it is not modded. It's 100% Vanilla 1.8.1 pre-3
The hosting company I go through requires the .jar to be named minecraft_server.jar
So I changed the name of the jar to that.
Not sure if that would cause that.

Something I've been noticing is a list of warnings that comes through every time these melons grow to a harvest-able state.
It shoots through the console with about 15-20 lines each one saying a melon was supposed to be at one coord and ended up at another coord.
I'll get the exact warning soon, but it went something like
melon was supposed to be at 10, -13, was 10, -12.
The melons are in spawn chunks. Could that cause something? I initially started to think it might have something to do with it considering the melons grow randomly based on a certain amount of ticks right?
Sorry if that's a dumb assumption, but the crash report is alien to me.

I can confirm that this happens to me, here are some crash logs on a server I run:

http://paste.debian.net/129339/
http://paste.debian.net/129341/
http://paste.debian.net/129342/
http://paste.debian.net/129343/

My server has crashed 10 times over the paste month with the exact same error but I noticed that the lines of code it says are the issue are slightly different sometimes (as in a line difference in the code).

This error has existed in 1.8, 1.8.1 pre1, 2 and 3.

Also, Sonic, I run a completely Vanilla server with no mods or anything and the crash report also says it cannot tell if it's modded or not, so a bug maybe?

Yeah exact same thing for me. I have about 12 of these since 1.8
Some times it can happen twice a day, other times it will happen once in three days.
If we can get either an explanation or a fix for this that would be great. I was thinking about reverting to the last snapshot since the error never occurred in that version.

Is this still a concern in the current Minecraft version 1.8.1 ?

Sorry, I couldn't tell you. I had so many issues with the vanilla server that I ditched it for Spigot 1.8. I will not be returning until they can get their crap together.
Good luck!

Ticket resolved as incomplete, because no answer in a reasonable amount of time (1+ year), if it still happens, please update the ticket.

I clearly stated I gave up and moved on. Several versions later and I have not had an issue like this. Consider it resolved I suppose.