/playsound does not check if sound exists.

Using the /playsound command on a non-existing sound succeeds, even though it does not exist

 

This creates a warning in output, meaning that it was detected that it wasn't a sound (and is unplayable), unlike handled errors like incomplete commands

 

fixing this will also:

1: allow for resource pack self-tests in the press of a button (using conditional command blocks, detect if resource pack is installed via a new sound made by resource pack)

2: help mappers that may make a typo when spelling a sound from going crazy