fix: handle zero size (#1888)

pkg/artifactcache/handler.go

@@ -311,10 +311,13 @@ func (h *Handler) commit(w http.ResponseWriter, r *http.Request, params httprout
 
 	db.Close()
 
-	if err := h.storage.Commit(cache.ID, cache.Size); err != nil {
+	size, err := h.storage.Commit(cache.ID, cache.Size)
+	if err != nil {
 		h.responseJSON(w, r, 500, err)
 		return
 	}
+	// write real size back to cache, it may be different from the current value when the request doesn't specify it.
+	cache.Size = size
 
 	db, err = h.openDB()
 	if err != nil {