for demo blog picture upload a reliable helper method has to be created which
checks whether a multipart form contains file data or not.
in case someone edits a post which had an image before but no new one is
chosen the form is type multipart, it contains the according field (of type file input)
but the req.body does not contain the file data
for demo blog picture upload a reliable helper method has to be created which checks whether a multipart form contains file data or not.
in case someone edits a post which had an image before but no new one is chosen the form is type multipart, it contains the according field (of type file input) but the req.body does not contain the file data