无法生成PDF文件与'0x' varbinary值ASP.net itextsharp

I have developed a webapp which is able to generate PDF files. The users have the choice to upload up to 5 pictures. When the users uploaded 5 pictures, I will then be able to generate the PDF file. However, if the users only chooses to upload 4, i will not be able to generated the PDF file and i will receive this error.I have developed a webapp which is able to gene