Improve error message

src/frontend/parse.c

@@ -88,7 +88,7 @@ checkvalid(struct pnode *pn)
                             pn->pn_value->v_name);
                 else
                     fprintf(cp_err,
-                            "Error(parse.c--checkvalid): %s: no such vector.\n",
+                            "Error(parse.c--checkvalid): %s: zero length vector.\n",
                             pn->pn_value->v_name);
                 return (FALSE);
             }

src/frontend/plotting/plotit.c

@@ -777,7 +777,7 @@ bool plotit(wordlist *wl, const char *hcopy, const char *devname)
     /* Now check for 0-length vectors. */
     for (d = vecs; d; d = d->v_link2) {
         if (!d->v_length) {
-            fprintf(cp_err, "Error(plotit.c--plotit): %s: no such vector\n",
+            fprintf(cp_err, "Error(plotit.c--plotit): %s: zero length vector\n",
                     d->v_name);
             goto quit;
         }