Skip elements that cannot be extracted and do not process them
Fixes https://demo.arkindex.org/process/ff0ff5d9-d2de-40b9-a1b7-f67ced70d074/0
This issues occurs when the line_image_extractor
cannot extract the polygon on the image. This is mostly about non-relevant elements with no transcriptions anyway. That's why I skip these kinds of elements.