Correctly display accounts without name.

lib/pleroma/web/mastodon_api/views/account_view.ex

@@ -18,7 +18,7 @@ def render("account.json", %{user: user}) do
       id: to_string(user.id),
       username: hd(String.split(user.nickname, "@")),
       acct: user.nickname,
-      display_name: user.name,
+      display_name: user.name || user.nickname,
       locked: false,
       created_at: Utils.to_masto_date(user.inserted_at),
       followers_count: user_info.follower_count,