References: Fixed references count/list recycle bin interaction

Count and reference list would get references then attempt to load
entities, which could fail to load if in the recycle bin.
This updates the queries to effectively ignore references for items we
can't see (in recycle bin).
Added test to cover.

For #4918

app/References/ReferenceFetcher.php

@@ -41,7 +41,8 @@ protected function queryReferencesToEntity(Entity $entity): Builder
     {
         $baseQuery = Reference::query()
             ->where('to_type', '=', $entity->getMorphClass())
-            ->where('to_id', '=', $entity->id);
+            ->where('to_id', '=', $entity->id)
+            ->whereHas('from');
 
         return $this->permissions->restrictEntityRelationQuery(
             $baseQuery,

tests/References/ReferencesTest.php

@@ -271,7 +271,31 @@ public function test_description_links_from_book_chapter_shelf_updated_on_url_ch
         }
     }
 
-    protected function createReference(Model $from, Model $to)
+    public function test_reference_from_deleted_item_does_not_count_or_show_in_references_page()
+    {
+        $page = $this->entities->page();
+        $referencingPageA = $this->entities->page();
+        $referencingPageB = $this->entities->page();
+
+        $this->asEditor();
+        $this->createReference($referencingPageA, $page);
+        $this->createReference($referencingPageB, $page);
+
+        $resp = $this->get($page->getUrl());
+        $resp->assertSee('Referenced by 2 items');
+
+        $this->delete($referencingPageA->getUrl());
+
+        $resp = $this->get($page->getUrl());
+        $resp->assertSee('Referenced by 1 item');
+
+        $resp = $this->get($page->getUrl('/references'));
+        $resp->assertOk();
+        $resp->assertSee($referencingPageB->getUrl());
+        $resp->assertDontSee($referencingPageA->getUrl());
+    }
+
+    protected function createReference(Model $from, Model $to): void
     {
         (new Reference())->forceFill([
             'from_type' => $from->getMorphClass(),