Null Pointer Exception

[WARNING] Failed to handle packet: java.lang.NullPointerException
java.lang.NullPointerException
	at com.bergerkiller.bukkit.sl.VirtualSign.get(VirtualSign.java:48)
	at com.bergerkiller.bukkit.sl.VirtualSign.get(VirtualSign.java:57)
	at com.bergerkiller.bukkit.sl.TileEntityVirtualSign.l(TileEntityVirtualSign.java:48)
	at net.minecraft.server.EntityPlayer.a(EntityPlayer.java:318)
	at net.minecraft.server.EntityPlayer.b(EntityPlayer.java:261)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:305)
	at net.minecraft.server.Packet10Flying.a(SourceFile:126)
	at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:92)
	at net.minecraft.server.NetworkListenThread.a(SourceFile:108)
	at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:471)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:374)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)