Fix: #442 カスタム絵文字のaliasesにnullが入る場合がある (#443)

* Fix: #442 カスタム絵文字のaliasesにnullが入る場合がある

* Fix test

* WebのほうにもNULLチェックを追加

* ローカルのエイリアス名を編集するところもついでにスリムに

spec/serializers/rest/custom_emoji_serializer_spec.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe REST::CustomEmojiSerializer do
+  let(:serialization) { serialized_record_json(record, described_class) }
+  let(:record) do
+    Fabricate(:custom_emoji, shortcode: 'ohagi', aliases: aliases)
+  end
+  let(:aliases) { [] }
+
+  context 'when empty aliases' do
+    it 'returns normalized aliases' do
+      expect(serialization['aliases']).to eq []
+    end
+  end
+
+  context 'when null aliases' do
+    let(:aliases) { nil }
+
+    it 'returns normalized aliases' do
+      expect(serialization['aliases']).to eq []
+    end
+  end
+
+  context 'when aliases contains null' do
+    let(:aliases) { [nil] }
+
+    it 'returns normalized aliases' do
+      expect(serialization['aliases']).to eq []
+    end
+  end
+
+  context 'when aliases contains normal text' do
+    let(:aliases) { ['neko'] }
+
+    it 'returns normalized aliases' do
+      expect(serialization['aliases']).to eq ['neko']
+    end
+  end
+end