Turn an assert into two more descriptive errors.

hlink.c

@@ -543,7 +543,14 @@ void finish_hard_link(struct file_struct *file, const char *fname, int fin_ndx,
 	if (inc_recurse) {
 		int gnum = F_HL_GNUM(file);
 		struct ht_int32_node *node = hashtable_find(prior_hlinks, gnum, 0);
-		assert(node != NULL && node->data != NULL);
+		if (node == NULL) {
+			rprintf(FERROR, "Unable to find a hlink node for %d (%s)\n", gnum, f_name(file, prev_name));
+			exit_cleanup(RERR_MESSAGEIO);
+		}
+		if (node->data == NULL) {
+			rprintf(FERROR, "Hlink node data for %d is NULL (%s)\n", gnum, f_name(file, prev_name));
+			exit_cleanup(RERR_MESSAGEIO);
+		}
 		assert(CVAL(node->data, 0) == 0);
 		free(node->data);
 		if (!(node->data = strdup(our_name)))