VLCMetadata: Check the media's video tracks count when available

This merge request brings a fix to the metadata update:

• If the media object is available when updating the metadata, its video tracks count is checked in order to update the isAudioOnly property.

Closes #1551 (closed)

changed milestone to %3.4.0

added Player Regression labels

mentioned in merge request !972 (merged)

approved this merge request

merged