Failed to load data for block entity Sign : java.lang.NullPointerException

Hello,

My problem is : I put my map on a Minecraft server (minecraft_server.1.9-pre4.jar), I start the server, the start but I get this error message in the console or when I try to join the server :

[16:23:01] [Server thread/ERROR]: Failed to load data for block entity Sign
java.lang.NullPointerException
	at aqn$1.h(SourceFile:99) ~[minecraft_server.1.9-pre4.jar:?]
	at ex.a(SourceFile:38) ~[minecraft_server.1.9-pre4.jar:?]
	at ev.a(SourceFile:37) ~[minecraft_server.1.9-pre4.jar:?]
	at aqn.a(SourceFile:107) ~[minecraft_server.1.9-pre4.jar:?]
	at apv.a(SourceFile:108) [minecraft_server.1.9-pre4.jar:?]
	at ass.a(SourceFile:306) [minecraft_server.1.9-pre4.jar:?]
	at ass.a(SourceFile:83) [minecraft_server.1.9-pre4.jar:?]
	at ass.a(SourceFile:70) [minecraft_server.1.9-pre4.jar:?]
	at lo.f(SourceFile:124) [minecraft_server.1.9-pre4.jar:?]
	at lo.c(SourceFile:76) [minecraft_server.1.9-pre4.jar:?]
	at lo.d(SourceFile:91) [minecraft_server.1.9-pre4.jar:?]
	at net.minecraft.server.MinecraftServer.l(SourceFile:325) [minecraft_server.1.9-pre4.jar:?]
	at net.minecraft.server.MinecraftServer.a(SourceFile:296) [minecraft_server.1.9-pre4.jar:?]
	at la.j(SourceFile:226) [minecraft_server.1.9-pre4.jar:?]
	at net.minecraft.server.MinecraftServer.run(SourceFile:427) [minecraft_server.1.9-pre4.jar:?]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_73]
[16:23:01] [Server thread/ERROR]: Failed to load data for block entity Sign
java.lang.NullPointerException
	at aqn$1.h(SourceFile:99) ~[minecraft_server.1.9-pre4.jar:?]
	at ex.a(SourceFile:38) ~[minecraft_server.1.9-pre4.jar:?]
	at ev.a(SourceFile:37) ~[minecraft_server.1.9-pre4.jar:?]
	at aqn.a(SourceFile:107) ~[minecraft_server.1.9-pre4.jar:?]
	at apv.a(SourceFile:108) [minecraft_server.1.9-pre4.jar:?]
	at ass.a(SourceFile:306) [minecraft_server.1.9-pre4.jar:?]
	at ass.a(SourceFile:83) [minecraft_server.1.9-pre4.jar:?]
	at ass.a(SourceFile:70) [minecraft_server.1.9-pre4.jar:?]
	at lo.f(SourceFile:124) [minecraft_server.1.9-pre4.jar:?]
	at lo.c(SourceFile:76) [minecraft_server.1.9-pre4.jar:?]
	at lo.d(SourceFile:91) [minecraft_server.1.9-pre4.jar:?]
	at net.minecraft.server.MinecraftServer.l(SourceFile:325) [minecraft_server.1.9-pre4.jar:?]
	at net.minecraft.server.MinecraftServer.a(SourceFile:296) [minecraft_server.1.9-pre4.jar:?]
	at la.j(SourceFile:226) [minecraft_server.1.9-pre4.jar:?]
	at net.minecraft.server.MinecraftServer.run(SourceFile:427) [minecraft_server.1.9-pre4.jar:?]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_73]

As you can see, I get this error two times.

I put the map and the full log on the attachment.

Note : I'm French, so sorry for my bad English.
Thanks you in advance et goodbye !