Remove icon from error dialog message box
Remove icon from error dialog message box

It looked awful when the error message is longer than one line and even
with a single line it looks better without it.

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