The User Media object never worked on CocoonJS, because CocoonJS does not support the HTML5 standard for video capture. For a short time we had experimental support using the custom CocoonJS API, but it was buggy (rotated 90 degrees on Android) and didn't support any useful features like taking screenshots. Since it was broken and not useful in any way, we removed support for it.
You're right that it shouldn't break the app just by being present though - that's fixed in the next build, but it still isn't supported.