Hi R²,
I don’t have TW v5.2.1 empty file so I can’t test exactly your environment.
I only could validate this (firefox latest):
- open tiddlywiki.com
- download empty.html
- open empty.html
- open Mermaid TW5 Plugin — http://github.com/efurlanm/mermaid-tw5 in another tab
- drag and drop the plugin link onto empty.html
- save and reload
- create a new tiddler and paste above example code in its body
- save, click on A or B => missing tiddlers “Tiddler A” and “Tiddler B” open.
Did the error occur on a new TW or in one of your wikis? Are any other plugins installed?
Fred