Set empty array instead of null to mediaIds property of posts

src/client/app/mobile/views/components/post-detail.vue

@@ -42,7 +42,7 @@
 			<div class="tags" v-if="p.tags && p.tags.length > 0">
 				<router-link v-for="tag in p.tags" :key="tag" :to="`/search?q=#${tag}`">{{ tag }}</router-link>
 			</div>
-			<div class="media" v-if="p.media">
+			<div class="media" v-if="p.media.length > 0">
 				<mk-media-list :media-list="p.media"/>
 			</div>
 			<mk-poll v-if="p.poll" :post="p"/>

src/client/app/mobile/views/components/post.vue

@@ -40,7 +40,7 @@
 					<mk-post-html v-if="p.ast" :ast="p.ast" :i="os.i" :class="$style.text"/>
 					<a class="rp" v-if="p.repost != null">RP:</a>
 				</div>
-				<div class="media" v-if="p.media">
+				<div class="media" v-if="p.media.length > 0">
 					<mk-media-list :media-list="p.media"/>
 				</div>
 				<mk-poll v-if="p.poll" :post="p" ref="pollViewer"/>

src/client/app/mobile/views/components/sub-post-content.vue

@@ -5,7 +5,7 @@
 		<mk-post-html v-if="post.ast" :ast="post.ast" :i="os.i"/>
 		<a class="rp" v-if="post.repostId">RP: ...</a>
 	</div>
-	<details v-if="post.media">
+	<details v-if="post.media.length > 0">
 		<summary>({{ post.media.length }}個のメディア)</summary>
 		<mk-media-list :media-list="post.media"/>
 	</details>