2 references title when switching between editors

[mariesosa]

Description

A useless reference title is added when switching between the editors. Leading to 2 references title being printed.

Step to reproduce

1. Add a reference with the plugin in the markdown editor.
2. Switch to the other editor.
3. Make any change (does not have to be related to references).
4. Go back to the markdown editor.

Versions

• Joplin : v2.7.15
• BibTeX plugin : v0.5.0