CraftBukkit Scoreboard crash

Sometimes, when a player logs onto a server, the scoreboard is not properly sent. This can result in a client-side NullPointerException when the Scoreboard display slot is set for an objective already in that exact same slot.
Here is an example stacktrace:
```
java.lang.NullPointerException
at arj.k(SourceFile:133)
at bdl.a(SourceFile:1086)
at fc.a(SourceFile:43)
at ci.b(SourceFile:350)
at bdl.d(SourceFile:95)
```
Here is an example data dump of the client's Scoreboard when this occurs:
```
a{}
b{}
c{Riking={null=arg@dbe848}}
d[null, null, null]
e{}
f{}
```
Here is an example data dump of the client's scoreboard in proper conditions:
```
a{health=are@9befde}
b{arl@35f5cb=[are@9befde]}
c{Mattman1153={are@9befde=arg@ff742e}, Wolvereness={are@9befde=arg@1249f80}, Riking={are@9befde=arg@163985e}}
d[null, are@9befde, null]
e{Orange-Red=arf@1a87752, Yeller=arf@131e0bc, Periwinkle=arf@1997f42}
f{Mattman1153=arf@1997f42, Wolvereness=arf@1a87752}
```

The cause of this is unknown as of April 2.
Any additional information is appreciated.