[FIX] Exception in contrib pdf when logo not image
[FIX] Exception in contrib pdf when logo not image

- Catch the exception and generate the pdf without the logo.
- Closes #884.

ThiefMaster/indico,mvidalgarcia/indico,indico/indico,OmeGak/indico,indico/indico,DirkHoffmann/indico,DirkHoffmann/indico,mic4ael/indico,ThiefMaster/indico,ThiefMaster/indico,DirkHoffmann/indico,mvidalgarcia/indico,mvidalgarcia/indico,mvidalgarcia/indico,mic4ael/indico,indico/indico,OmeGak/indico,pferreir/indico,DirkHoffmann/indico,indico/indico,mic4ael/indico,pferreir/indico,pferreir/indico,OmeGak/indico,pferreir/indico,ThiefMaster/indico,OmeGak/indico,mic4ael/indico