Affects Version/s: Minecraft 1.12.2, Minecraft 17w43a, Minecraft 17w43b
Fix Version/s: None
The Playsound command has the following syntax:
/playsound <sound> <source> <player> [x] [y] [z] [volume] [pitch] [minVolume]
/playsound <sound> <source> and leaving out <player> causes an internal server error to happen.
Simple fix is to improve the argument validation.