Bugfix: Sound player delays dropping subsequent sounds

[avanwinkle]

A bug was discovered in MPF-MC SoundPlayer where adding a sound with delay would end the sound player processing loop, potentially discarding additional sounds passed in the same payload.

This is because the delay check calls return instead of continue, thus aborting the loop through all sounds passed.

This PR changes the call to continue, as well as for a few other error checks that also called return and would prevent subsequent sounds in the payload from playing.

Manually tested.