fix: paste of nonexist block not handled

close #1720

src/main/frontend/db/outliner.cljs

@@ -1,5 +1,6 @@
 (ns frontend.db.outliner
   (:require [datascript.core :as d]
+            [frontend.db :as db]
             [frontend.db.react :as react]
             [frontend.util :as util]
             [frontend.debug :as debug]
@@ -54,3 +55,7 @@
                  [?a :block/journal? true]]
                @conn)]
     (flatten r)))
+
+(defn remove-non-existed-refs!
+  [refs]
+  (filter db/entity refs))

src/main/frontend/modules/outliner/core.cljs

@@ -130,6 +130,7 @@
     (let [m (-> (:data this)
                 (dissoc :block/children :block/dummy? :block/meta)
                 (util/remove-nils))
+          m (update m :block/refs db-outliner/remove-non-existed-refs!)
           other-tx (:db/other-tx m)]
       (when (seq other-tx)
         (swap! txs-state (fn [txs]