Gets the data object that was passed to a popup.
Note: The terms popup and lightbox refer to the same element. While the editor and dashboard now refer to it as a popup, the API methods continue to use the term lightbox for backward compatibility. The documentation uses both terms accordingly.
Retrieves the data object, if any, that was passed when a popup
was opened with the openLightbox() method.
If a popup was opened in any other way, getContext() returns undefined.
To pass data to a popup, it must be opened programmatically using the openLightbox()
method. Popups that are opened automatically on page load, or with a link from a page element don't receive passed data.