QtMultimedia aborts when not supported

When using QtMultimedia on an "unsupported platform" (or forgot to build it with any backend) it will qFatal and forcefully end your application.

Especially with QML this is undesirable. It should print a warning and/or provide a way to query backend capabilities but not just flat out let my application die.

QDummyIntegration() { qFatal("QtMultimedia is not currently supported on this platform or compile
r."); }