Polish debug code

src/fellow_cache.c

@@ -4403,8 +4403,10 @@ fellow_busy_log_submit(const struct fellow_busy *fbo)
 
 	n = fellow_obj_regions(fbo->fc->ffd, fbo->fco, region);
 	assert(n == fbo->nregion);
-	qsort(fbo->region, n, sizeof(struct buddy_off_extent), fdr_compar);
-	qsort(region, n, sizeof(struct buddy_off_extent), fdr_compar);
+	qsort(((struct fellow_busy *)fbo)->region,
+	    (size_t)n, sizeof(struct buddy_off_extent), fdr_compar);
+	qsort(region,
+	    (size_t)n, sizeof(struct buddy_off_extent), fdr_compar);
 	for (r = 0; r < n; r++) {
 		assert(region[r].off == fbo->region[r].off);
 		assert(region[r].size == fbo->region[r].size);