Entering a single colon (:) in the Direct Connect menu crashes the game

Steps to reproduce:

1. Open the "Direct Connect" menu.
2. Enter ":" in the "IP Adress" field.
3. Press Enter to connect.
4. Observe crash

What did I expect to happen?

I expected the game to do nothing or show me a message that I entered an invalid address.

Stacktrace:
```

Description: keyPressed event handler

java.lang.ArrayIndexOutOfBoundsException: 0

at crh.a(SourceFile:61)

at cjj.<init>(SourceFile:35)

at clw.a(SourceFile:332)

at clw.confirmResult(SourceFile:210)

at cjo.h(SourceFile:65)

at cjo.keyPressed(SourceFile:91)

at cfp.a(SourceFile:389)

at ckc.a(SourceFile:430)

at cfp.a(SourceFile:387)

at org.lwjgl.glfw.GLFWKeyCallbackI.callback(GLFWKeyCallbackI.java:37)

at org.lwjgl.system.JNI.invokeV(Native Method)

at org.lwjgl.glfw.GLFW.glfwPollEvents(GLFW.java:3029)

at cgc.a(SourceFile:309)

at cfs.c(SourceFile:875)

at cfs.a(SourceFile:395)

at net.minecraft.client.main.Main.main(SourceFile:144)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:498)

at org.multimc.onesix.OneSixLauncher.launchWithMainClass(OneSixLauncher.java:196)

at org.multimc.onesix.OneSixLauncher.launch(OneSixLauncher.java:231)

at org.multimc.EntryPoint.listen(EntryPoint.java:143)

at org.multimc.EntryPoint.main(EntryPoint.java:34)

```