Send back proper error response if xquery source file could not be found.
Send back proper error response if xquery source file could not be found.

svn path=/trunk/eXist-1.0/; revision=1993

lcahlander/exist,kohsah/exist,patczar/exist,MjAbuz/exist,kohsah/exist,windauer/exist,wolfgangmm/exist,dizzzz/exist,opax/exist,zwobit/exist,shabanovd/exist,MjAbuz/exist,RemiKoutcherawy/exist,wolfgangmm/exist,ambs/exist,jessealama/exist,patczar/exist,hungerburg/exist,ljo/exist,olvidalo/exist,jessealama/exist,RemiKoutcherawy/exist,kohsah/exist,ambs/exist,RemiKoutcherawy/exist,ljo/exist,joewiz/exist,eXist-db/exist,MjAbuz/exist,opax/exist,olvidalo/exist,ambs/exist,ljo/exist,joewiz/exist,eXist-db/exist,wshager/exist,hungerburg/exist,opax/exist,jensopetersen/exist,RemiKoutcherawy/exist,ambs/exist,zwobit/exist,adamretter/exist,shabanovd/exist,MjAbuz/exist,wolfgangmm/exist,ambs/exist,eXist-db/exist,zwobit/exist,dizzzz/exist,joewiz/exist,wshager/exist,patczar/exist,jessealama/exist,hungerburg/exist,wolfgangmm/exist,wolfgangmm/exist,windauer/exist,shabanovd/exist,joewiz/exist,jensopetersen/exist,joewiz/exist,windauer/exist,ambs/exist,kohsah/exist,olvidalo/exist,opax/exist,wolfgangmm/exist,eXist-db/exist,patczar/exist,hungerburg/exist,joewiz/exist,wshager/exist,patczar/exist,dizzzz/exist,zwobit/exist,MjAbuz/exist,zwobit/exist,wshager/exist,RemiKoutcherawy/exist,olvidalo/exist,MjAbuz/exist,lcahlander/exist,lcahlander/exist,adamretter/exist,adamretter/exist,zwobit/exist,jensopetersen/exist,shabanovd/exist,hungerburg/exist,ljo/exist,adamretter/exist,jensopetersen/exist,jessealama/exist,wshager/exist,jensopetersen/exist,ljo/exist,eXist-db/exist,olvidalo/exist,kohsah/exist,shabanovd/exist,jensopetersen/exist,kohsah/exist,wshager/exist,opax/exist,shabanovd/exist,jessealama/exist,windauer/exist,RemiKoutcherawy/exist,lcahlander/exist,lcahlander/exist,ljo/exist,adamretter/exist,windauer/exist,dizzzz/exist,jessealama/exist,windauer/exist,adamretter/exist,dizzzz/exist,patczar/exist,dizzzz/exist,eXist-db/exist,lcahlander/exist