[MC-122754] Potion ID with caps crashes game

The bug

/giving yourself a potion with a proper "Potion" tag, but with caps, will crash your game.

For Example:

/give @p minecraft:potion{Potion:"swiftness"}

gives you a potion with swiftness, but

/give @p minecraft:potion{Potion:"Swiftness"}

will immediately crash your game.

This doesn't work for invalid potion id's, like "potato".
Along with that, spawning in a container with the potion in it will crash you the instant you check the contents of the container.

EDIT: Writing any potion ID, valid or invalid, with caps seems to crash your game

Crash report

17w48a: crash-2017-11-30_18.36.37-client.txt

Description: Rendering entity in world

java.lang.IllegalArgumentException: Non [a-z0-9/._-] character in path of location: minecraft:Swiftness
	at mq.<init>(SourceFile:31)
	at mq.<init>(SourceFile:36)
	at anm.a(SourceFile:27)
	at ano.c(SourceFile:133)
	at ano.d(SourceFile:125)
	at ano.c(SourceFile:82)
	at bnb$4.getColor(SourceFile:81)
	at bnb.a(SourceFile:117)
	at cem.a(SourceFile:180)
	at cem.a(SourceFile:98)
	at cem.a(SourceFile:80)
	at cem.a(SourceFile:116)
	at cek.a(SourceFile:142)
	at cek.a(SourceFile:18)
	at cdv.a(SourceFile:362)
	at cdv.a(SourceFile:349)
	at bzo.a(SourceFile:614)
	at bzi.b(SourceFile:1185)
	at bzi.a(SourceFile:1093)
	at bzi.a(SourceFile:951)
	at bmm.b(SourceFile:820)
	at bmm.a(SourceFile:381)
	at net.minecraft.client.main.Main.main(SourceFile:134)