Demo page issue with iPhone

Hi I would like to use the ajax uploade. Before instalation I tried your demo page on an iPhone SE with Safari in Private Mode. It showed a Inernal Server Error code 500 when I try to upload a photo from the phone. The photo seems to work in the list but not on the normal upload field in your form
Could you please have a look it is may be a bug in your ajax uploader or your demo page. Would like to better understand if the same will happen if I use your plugin on my side.
Regards
Jochen