Fix crashing bug

This fixes a crashing bug in the scraper on the rare occasion when the attachment is not a PDF.  

An example with a TIF attachment is here http://oakland.legistar.com/LegislationDetail.aspx?ID=1144399&GUID=E439AA64-1A48-43C7-998F-71CEC1CD2342&Options=ID|Text|&Search=fmc071012