When the user closes the Minecraft client instead of disconnecting, it generates an error:

User disconnects (all server types):
2012-10-26 11:11:14 [INFO] MichaelGrue[/127.0.0.1:54749] logged in with entity id 676 at (-64.5, 71.0, 250.5)
2012-10-26 11:11:18 [INFO] MichaelGrue lost connection: disconnect.quitting

When closing Minecraft client (Windows 7 with Java Jar file):
2012-10-26 11:12:02 [INFO] MichaelGrue[/127.0.0.1:54783] logged in with entity id 1131 at (-64.5, 71.0, 250.5)
java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at java.io.FilterInputStream.read(Unknown Source)
at anq.a(Unknown Source)
at anq.read(Unknown Source)
at java.io.FilterInputStream.read(Unknown Source)
at dx.a(SourceFile:177)
at bx.i(SourceFile:248)
at bx.c(SourceFile:23)
at by.run(SourceFile:101)
2012-10-26 11:12:08 [INFO] MichaelGrue lost connection: disconnect.genericReason

When closing Minecraft client (Windows 7 with Exe file):
[INFO] MichaelGrue[/127.0.0.1:54850] logged in with entity id 496 at (-64.5, 71.0, 250.5)
[INFO] MichaelGrue lost connection: disconnect.genericReason

When closing Minecraft client (Ubuntu with Java Jar):
2012-10-26 11:16:08 [INFO] MichaelGrue[/93.162.xx.xx:54940] logged in with entity id 411200 at (-372.2981611096897, 82.0, 1614.4755745429802)
java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:168)
at java.io.FilterInputStream.read(FilterInputStream.java:116)
at anq.a(Unknown Source)
at anq.read(Unknown Source)
at java.io.FilterInputStream.read(FilterInputStream.java:66)
at dx.a(SourceFile:177)
at bx.i(SourceFile:248)
at bx.c(SourceFile:23)
at by.run(SourceFile:101)
2012-10-26 11:16:13 [INFO] MichaelGrue lost connection: disconnect.genericReason

Expects:
The same as when running Windows EXE file:

[INFO] MichaelGrue[/127.0.0.1:54850] logged in with entity id 496 at (-64.5, 71.0, 250.5)
[INFO] MichaelGrue lost connection: disconnect.genericReason