wasapi: Fix runtime/build warnings
wasapi: Fix build warnings
gstwasapiutil.c(173) : warning C4715: 'gst_wasapi_device_role_to_erole': not all control paths return a value
gstwasapiutil.c(188) : warning C4715: 'gst_wasapi_erole_to_device_role': not all control paths return a value
wasapi: Don't cast GstDeviceProvider to GstElement
The GstDeviceProvider isn't subclass of GstElement.
(gst-device-monitor-1.0:49356): GLib-GObject-WARNING **: 20:21:18.651:
invalid cast from 'GstWasapiDeviceProvider' to 'GstElement'