Only write annotations if there are annotations

[ealgase]

Please follow the guide below

• You will be asked some questions and requested to provide some information, please read them carefully and answer honestly
• Put an x into all the boxes [ ] relevant to your issue (like this: [x])
• Use the Preview tab to see what your issue will actually look like

---

Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2018.12.17. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

• I've verified and I assure that I'm running youtube-dl 2018.12.17

Before submitting an issue make sure you have:

• At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones
• Checked that provided video/audio/playlist URLs (if any) are alive and playable in a browser

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)
• Site support request (request for adding support for a new site)
• Feature request (request for a new functionality)
• Question
• Other

---

Description of your issue, suggested solution and other information

I often archive many youtube videos, as well as videos from other websites. My general purpose command includes the --write-annotations flag. However, this ends up writing many empty annotations.xml files. A flag to only write annotations if they exist (or building that into the existing flag) would be very useful.