warning and checks for noimpostor children (#12482)
warning and checks for noimpostor children (#12482)

* warning and checks for noimpostor children

* error message in viewer

* Update packages/dev/core/src/Debug/physicsViewer.ts

* removed empty line to kick a new build

Co-authored-by: Cedric Guillemet <6978064c39c586f803934a265f0429d91ca49b31@microsoft.com>
Co-authored-by: David Catuhe <82bae252544aba2dfdfafbf46d91f2f39cf89677@live.fr>
BabylonJS/Babylon.js,sebavan/Babylon.js,RaananW/Babylon.js,sebavan/Babylon.js,sebavan/Babylon.js,BabylonJS/Babylon.js,RaananW/Babylon.js,RaananW/Babylon.js,BabylonJS/Babylon.js