fix: Avoid crashing the site when trying to delete a translation

src/RevisionGraphStorage.php

@@ -62,13 +62,20 @@ class RevisionGraphStorage {
       $branch = $parent_version_id;
     }
 
-    $this->connection->insert('revision_graph')->fields([
-      'primary_id' => $entity->id(),
-      'version_id' => $entity->getRevisionId(),
-      'parent_version_id' => $parent_version_id,
-      'type' => $entity->getEntityTypeId(),
-      'branch' => $this->formatBranchName($branch, $entity->language()->getId()),
-    ])->execute();
+    $result = $this->connection->query("SELECT * FROM {revision_graph} WHERE primary_id = :primary_id AND version_id = :version_id AND type = :type", [
+      ':primary_id' => $entity->id(),
+      ':version_id' => $entity->getRevisionId(),
+      ':type' => $entity->getEntityTypeId(),
+    ])->fetchAll();
+    if (empty($result)) {
+      $this->connection->insert('revision_graph')->fields([
+        'primary_id' => $entity->id(),
+        'version_id' => $entity->getRevisionId(),
+        'parent_version_id' => $parent_version_id,
+        'type' => $entity->getEntityTypeId(),
+        'branch' => $this->formatBranchName($branch, $entity->language()->getId()),
+      ])->execute();
+    }
   }
 
   protected function formatBranchName($parent_branch, $language_id): string {