Fixed playback reset on resizing
Fixed playback reset on resizing

I removed the call to `.empty()`when handling the resize of the container when `responsive`is set to `true`.
This allow the playback to keep going while the container is resizing.
ffxsam/wavesurfer.js,katspaugh/wavesurfer.js,katspaugh/wavesurfer.js,ffxsam/wavesurfer.js