Loading a world created with a client using only ssp and loading it using ssp and olddays core result in a crash

[gus33000]

---- Minecraft Crash Report ----
// Sorry :(

Time: 03/05/14 09:38
Description: Unexpected error

java.lang.NullPointerException
at aiv.a(SourceFile:36)
at ain.a(SourceFile:87)
at aet.a(SourceFile:425)
at ssp.ChunkProvider.a(ChunkProvider.java:211)
at adr.a(SourceFile:732)
at ssp.ChunkProvider.c(ChunkProvider.java:120)
at ssp.ChunkProvider.d(ChunkProvider.java:134)
at ssp.WorldSSP.e(WorldSSP.java:507)
at acl.(SourceFile:32)
at bfa.a(SourceFile:114)
at bfl.a(RenderGlobal.java:1499)
at bfe.a(EntityRenderer.java:1269)
at bfe.b(EntityRenderer.java:1135)
at atv.S(Minecraft.java:902)
at atv.d(Minecraft.java:794)
at net.minecraft.client.main.Main.main(SourceFile:101)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Stacktrace:
at aiv.a(SourceFile:36)
at ain.a(SourceFile:87)
at aet.a(SourceFile:425)
at ssp.ChunkProvider.a(ChunkProvider.java:211)
at adr.a(SourceFile:732)
at ssp.ChunkProvider.c(ChunkProvider.java:120)
at ssp.ChunkProvider.d(ChunkProvider.java:134)
at ssp.WorldSSP.e(WorldSSP.java:507)
at acl.(SourceFile:32)
at bfa.a(SourceFile:114)
at bfl.a(RenderGlobal.java:1499)
at bfe.a(EntityRenderer.java:1269)
at bfe.b(EntityRenderer.java:1135)

-- Affected level --
Details:
Level name: Test
Chunk stats: ServerChunkCache: 301 Drop: 0
Level seed: 6054958565567688425
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: World: (100,64,405), Chunk: (at 4,4,5 in 6,25; contains blocks 96,0,400 to 111,255,415), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 175 game time, 175 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 128964 (now: false), thunder time: 37797 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at atv.b(Minecraft.java:2410)
at atv.d(Minecraft.java:814)
at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
Minecraft Version: 1.6.4
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 123295296 bytes (117 MB) / 250085376 bytes (238 MB) up to 954728448 bytes (910 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
AABB Pool Size: 41417 (2319352 bytes; 2 MB) allocated, 2 (112 bytes; 0 MB) used
Suspicious classes: mod_OldDays, IScrollingGui, GuiOldDaysBase, ...[ssp.WorldSSP, EntityPlayerSP2, FakeServer, ...]
IntCache: cache: 17, tcache: 0, allocated: 1, tallocated: 63
Launched Version: Test2
LWJGL: 2.9.0
OpenGL: Intel(R) HD Graphics 4600 GL version 4.2.0 - Build 10.18.10.3379, Intel
Is Modded: Definitely; Client brand changed to 'SSP 3.1 for 1.6.4; OldDays 4.1'
Type: Client (map_client.txt)
Resource Pack: Default
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 3013 (168728 bytes; 0 MB) allocated, 16 (896 bytes; 0 MB) used

And the folowing message was spammed in the console before the crash :
[CLIENT] [WARNING] Skipping Piece with id MSCorridorOld