Fixes #1481

Clear out pending errors on player disposal.
Source selection errors are dispatched asynchronously so that there is an opportunity to override the error message. If the player is disposed during that period, the error timeout wasn't being cleared properly. Fix for #1480.

Fix whitespace
When defining variables inline with declarations, stick to one variable per line.
Make sure the error property is set before proxying through the tech.
Some error events don't cause the error property on the video element to be set. In that case, handle the event like any other. Fixes #1465.
Added line to the changelog for #1482