Spectrogram pan stops working after zoom

[oliverroick]

How to reproduce

• Load a file
• Move the time indicator to the end
• Zoom in twice
• Pan the spectrogram
• Zoom out once
• Try panning the spectrogram

Expected behaviour

• While holding the mouse button down and moving the mouse the spectrogram should move accordingly

Actual behaviour

• The spectrogram doesn't move

[LanesGood]

@oliverroick this may be relevant: https://github.com/katspaugh/wavesurfer.js/issues/2406