rpki-client fail hard if repository is missing

[Claudio Jeker]

If parse_filepath() is unable to locate the repository then fail hard.
It makes no sense to limp along in this case because something bigger is
broken and it is better to know about that early.

-- 
:wq Claudio

Index: parser.c
===================================================================
RCS file: /cvs/src/usr.sbin/rpki-client/parser.c,v
retrieving revision 1.68
diff -u -p -r1.68 parser.c
--- parser.c    19 Apr 2022 09:52:29 -0000      1.68
+++ parser.c    19 Apr 2022 12:56:12 -0000
@@ -108,7 +108,7 @@ parse_filepath(unsigned int repoid, cons
        /* build file path based on repoid, entity path and filename */
        rp = repo_get(repoid);
        if (rp == NULL)
-               return NULL;
+               errx(1, "build file path: repository %u missing", repoid);
 
        if (loc == DIR_VALID)
                repopath = rp->validpath;