Avoid HLS desktop Safari crashes (#637)

Conditions for crash:
- hls source
- desktop browser - Safari, not tested with desktop Android
- splash setup
- preload != none

Caused by additional load event when preload != "none".

Solution: extend above conditional to
preload != "none" && video.type != "mpegurl"

The additional load is still triggered on devices where dataload is not
supported, e.g. iPad.