Show Focus Point stops with an error message on every first call

[capricorn8]

Starting with LrC 14 on Windows, the plug-in stops with an error message in MogrifyUtils on every first call for an image.
Subsequent calls will succeed in displaying the focus point.
Moving to the next image, same story.

[capricorn8]

Analysis and proposal for fix by John R. Ellis (LR SDK luminary on Adobe forums) in personal communication:

"The root cause of the issue is poorly designed concurrency architecture of the Lightroom SDK.

requestJpegThumbnail() appears to call the callback synchronously if the requested thumbnail is in an internal cache. Otherwise, it returns immediately and calls the callback asynchronously after the thumbnail is generated and loaded into the cache, which could take anywhere from 0.01 seconds to a couple seconds if the photo has to be re-rendered.

In order to make sure the thumbnail has been written to file before proceeding with the next steps, exportToDisk() should busy wait until the callback is invoked.

photo:getRawMetadata() has to be executed outside the callback, because this method "yields" which is not allowed in a no-yielding context (asynchronous call of callback)."