add entity to warning message for sound (fixes #2558)
add entity to warning message for sound (fixes #2558)

dmarcos/aframe,googlecreativelab/aframe,ngokevin/aframe,chenzlabs/aframe,mkungla/aframe,dmarcos/aframe,weddingdj/aframe,ngokevin/aframe,aframevr/aframe,aframevr/aframe,mkungla/aframe,RSpace/aframe,darkwing/aframe,RSpace/aframe,jaxmolina/ar,wizgrav/aframe,googlecreativelab/aframe,darkwing/aframe,wizgrav/aframe,chenzlabs/aframe,jaxmolina/ar,weddingdj/aframe