[BUG] Exception during heavy bot attack

**Describe the bug**
During a heavy bot attack, the following exceptions can be seen in Velocity logs:
```
[Netty epoll Worker #15/WARN] [io.netty.util.concurrent.AbstractEventExecutor]: A task raised an exception. Task: net.elytrium.limboapi.server.LimboImpl$$Lambda$2520/0x00000008015e9870@15db9198
java.lang.NullPointerException: Cannot invoke "com.velocitypowered.proxy.protocol.netty.MinecraftEncoder.setState(com.velocitypowered.proxy.protocol.StateRegistry)" because the return value of "io.netty.channel.ChannelPipeline.get(java.lang.Class)" is null
at com.velocitypowered.proxy.connection.MinecraftConnection.setState(MinecraftConnection.java:353) ~[velocity.jar:3.2.0-SNAPSHOT (git-01f1e1a9-b243)]
at net.elytrium.limboapi.server.LimboImpl.lambda$spawnPlayer$6(LimboImpl.java:233) ~[?:?]
at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:174) ~[velocity.jar:3.2.0-SNAPSHOT (git-01f1e1a9-b243)]
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:167) ~[velocity.jar:3.2.0-SNAPSHOT (git-01f1e1a9-b243)]
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:470) ~[velocity.jar:3.2.0-SNAPSHOT (git-01f1e1a9-b243)]
at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:403) ~[velocity.jar:3.2.0-SNAPSHOT (git-01f1e1a9-b243)]
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[velocity.jar:3.2.0-SNAPSHOT (git-01f1e1a9-b243)]
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[velocity.jar:3.2.0-SNAPSHOT (git-01f1e1a9-b243)]
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[velocity.jar:3.2.0-SNAPSHOT (git-01f1e1a9-b243)]
at java.lang.Thread.run(Thread.java:833) [?:?]
```

**To Reproduce**
View the console during heavy bot attack with bots that join and leave the server after a few seconds.

**Expected behavior**
No exception

**Screenshots**
None

**Server Info (please complete the following information):**
- LimboAPI 1.1.11 downloaded from GitHub releases
- LimboAuth 1.1.12 downloaded from GitHub releases
- LimboFilter 1.1.10 downloaded from GitHub releases

**Additional context**
None