Fix race condition bug in generateFigure()

[seav]

In the JS file eph-common.js, the generateFigure() function assumes that the <figcaption> that is the target of the AJAX operation is still attached to the document when the AJAX resolves. But the user may have switched the panel contents before the AJAX resolves leading to either the wrong photo attribution being added or not being able to attach the photo attribution.

The obvious solution is to update the function to refer to the panelElem Records field.