why i try to run a server this happens

---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 2/12/14 12:16 PM
Description: Exception in server tick loop

java.lang.NullPointerException: Exception in server tick loop
at net.minecraft.server.v1_7_R1.DedicatedServer.aw(DedicatedServer.java:282)
at net.minecraft.server.v1_7_R1.DedicatedServer.a(DedicatedServer.java:228)
at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:465)
at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617)

A detailed walkthrough of the error, its code path and all known details is as follows:
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-- System Details --
Details:
Minecraft Version: 1.7.2
Operating System: Windows 8 (x86) version 6.2
Java Version: 1.7.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 2177672 bytes (2 MB) / 16318464 bytes (15 MB) up to 129761280 bytes (123 MB)
JVM Flags: 1 total; -Xmx127M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
CraftBukkit Information:
  Running:
  Failed to handle CraftCrashReport:
java.lang.NullPointerException
at org.bukkit.Bukkit.getName(Bukkit.java:74)
at org.bukkit.craftbukkit.v1_7_R1.CraftCrashReport.call(CraftCrashReport.java:20)
at net.minecraft.server.v1_7_R1.CrashReportSystemDetails.a(SourceFile:74)
at net.minecraft.server.v1_7_R1.CrashReport.h(CrashReport.java:45)
at net.minecraft.server.v1_7_R1.CrashReport.<init>(CrashReport.java:33)
at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:474)
at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617)

Profiler Position: N/A (disabled)
Is Modded: ~~ERROR~~ NullPointerException: null
Type: Dedicated Server (map_server.txt)