Option to turn on/off automated creation of image when uploading PDF file

Hi Constant,

I regularly upload about 10 pdfs to use in my emails due to having multiple versions of our newsletter.  You have recently added a function that creates an automatic, one page jpg preview of the pdf.  In the past, I could simply drop all 10 files and they would upload.  With your new function, I cannot as the page regularly gets stuck and loops.  All I see is a Waiting for Cache message on the bottom status.  While this is a novel idea, I really dislike it because I do not use your auto-created image anyway.  Please roll this code back OR ad the option to make it optional so I can turn it off.  I cannot drop two pdfs due to it freezing.  While I am sure this was well intentioned, the process is not working for my account and I would like to remove it.

Sincerely,

Eric