If the exploit cannot fetch certain xref fields, we warn the user we don't like their PDF, and recommend them to try a different one.
This is a fix for issues related to: 'undefined method `' for nil:NilClass' It is possible that a PDF may not have the 'Size' xref, and people are running into the 'undefined method'' for NilClass' exception. Because the pdf parser always assumes there is a Size field, so it uses a match() function to find the value for Size, which can be nil. See the following bug report for example: https://dev.metasploit.com/redmine/issues/7014
This reverts commit 02e124a.
This reverts commit f479fae.