fix: send null for empty edited_at in mastodon api

packages/megalodon/src/pleroma/api_client.ts

@@ -357,6 +357,7 @@ namespace PleromaAPI {
       content: s.content,
       plain_content: s.pleroma.content?.['text/plain'] ? s.pleroma.content['text/plain'] : null,
       created_at: s.created_at,
+      edited_at: s.edited_at || null,
       emojis: Array.isArray(s.emojis) ? s.emojis.map(e => emoji(e)) : [],
       replies_count: s.replies_count,
       reblogs_count: s.reblogs_count,

packages/megalodon/src/pleroma/entities/status.ts

@@ -18,6 +18,7 @@ namespace PleromaEntity {
     reblog: Status | null
     content: string
     created_at: string
+    edited_at?: string | null
     emojis: Emoji[]
     replies_count: number
     reblogs_count: number