MSVC 14.0: Fix warning C4702: unreachable code

Change-Id: I38db92984daae40981f2d3f60c4efa38684d5328
Reviewed-on: https://gerrit.libreoffice.org/34382
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: David Ostrovsky <david@ostrovsky.org>

sax/source/fastparser/fastparser.cxx

@@ -980,7 +980,7 @@ bool FastSaxParserImpl::consume(EventList *pEventList)
                 return false;
             case EXCEPTION:
                 rEntity.throwException( mxDocumentLocator, false );
-                return false;
+                SAL_FALLTHROUGH; // avoid unreachable code warning with some comilers
             default:
                 assert(false);
                 return false;