[MC-122317] Game crashes when a colon is entered after a slash or another colon in commands

The bug

When a colon is entered after a slash or another colon, the game will crash.

How to reproduce

Typing out the following commands will cause the game to crash:

/give @s minecraft::

/function example/:

Crash report

17w47b: crash-2017-11-23_21.20.48-client.txt

Description: charTyped event handler

java.lang.IllegalArgumentException: Non [a-z0-9/._-] character in path of location: minecraft::
	at mp.<init>(SourceFile:31)
	at mp.<init>(SourceFile:36)
	at mp.a(SourceFile:121)
	at cg.d(SourceFile:156)
	at cg.a(SourceFile:69)
	at cf.a(SourceFile:21)
	at cf.parse(SourceFile:14)
	at com.mojang.brigadier.tree.ArgumentCommandNode.parse(ArgumentCommandNode.java:55)
	at com.mojang.brigadier.CommandDispatcher.parseNodes(CommandDispatcher.java:169)
	at com.mojang.brigadier.CommandDispatcher.parseNodes(CommandDispatcher.java:191)
	at com.mojang.brigadier.CommandDispatcher.parseNodes(CommandDispatcher.java:191)
	at com.mojang.brigadier.CommandDispatcher.parse(CommandDispatcher.java:143)
	at bpd.h(SourceFile:161)
	at bpd.a(SourceFile:97)
	at bpd$$Lambda$587/1093383199.accept(Unknown Source)
	at bnm.a(SourceFile:145)
	at bnm.b(SourceFile:140)
	at bnm.charTyped(SourceFile:383)
	at boi.charTyped(SourceFile:40)
	at bme.a(SourceFile:360)
	at bme$$Lambda$593/430092836.run(Unknown Source)
	at bqb.a(SourceFile:428)
	at bme.a(SourceFile:360)
	at bme$$Lambda$111/1323828508.invoke(Unknown Source)
	at org.lwjgl.glfw.GLFWCharModsCallbackI.callback(GLFWCharModsCallbackI.java:23)
	at org.lwjgl.system.JNI.invokeV(Native Method)
	at org.lwjgl.glfw.GLFW.glfwPollEvents(GLFW.java:2520)
	at bmr.a(SourceFile:282)
	at bmh.b(SourceFile:843)
	at bmh.a(SourceFile:376)
	at net.minecraft.client.main.Main.main(SourceFile:134)