Errors thrown during PlayerLoginEvent put FML into a bad state; errors get swallowed

[skyboy]

Specifically, at line https://github.com/MinecraftForge/FML/blob/master/src/main/java/cpw/mods/fml/common/network/internal/FMLProxyPacket.java#L101 The dispatcher has not yet been set. A null check would probably suffice (I'm not familiar with the flow here), if it's not possible to assign the dispatcher earlier.