FIX: Don't notify of post deletion when agreeing with automatic flags. (#19241)

lib/post_destroyer.rb

@@ -330,6 +330,12 @@ class PostDestroyer
     allowed_user = @user.human? && @user.staff?
     return unless allowed_user && rs = reviewable.reviewable_scores.order('created_at DESC').first
 
+    # ReviewableScore#types is a superset of PostActionType#flag_types.
+    # If the reviewable score type is not on the latter, it means it's not a flag by a user and
+    #  must be an automated flag like `needs_approval`. There's no flag reason for these kind of types.
+    flag_type = PostActionType.flag_types[rs.reviewable_score_type]
+    return unless flag_type
+
     notify_responders = options[:notify_responders]
 
     Jobs.enqueue(
@@ -341,7 +347,7 @@ class PostDestroyer
         flagged_post_response_raw_content: @post.raw,
         url: notify_responders ? options[:parent_post].url : @post.url,
         flag_reason: I18n.t(
-          "flag_reasons#{".responder" if notify_responders}.#{PostActionType.types[rs.reviewable_score_type]}",
+          "flag_reasons#{".responder" if notify_responders}.#{flag_type}",
           locale: SiteSetting.default_locale,
           base_path: Discourse.base_path
         )