Fix cycle/build with -al

assemble.pas, TExternalAssembler.WriteSourceLine:
  * don't generate an internal error if no module is found; if the system unit is compiled with -al there can be cases when fileinfo contains only zeros (though I wonder where this comes from; I'll need to investigate this when I have time)



git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@23631 3ad0048d-3df7-0310-abae-a5850022a9f2