Steps to reproduce:
- Open a page for reading, open your browser console.
- Click the editing tab to start editing in VE.
The editor is loaded without reloading the page (just updating the URL).
The page is loaded with &veaction=edit. When you enable "Stop on all errors" in your debugger, you will stop on "ve.isUnmodifiedLeftClick is undefined".
This seems to be caused by rEVED87ea771ae68e: Centralize some checks for unmodified left clicks, the ve.utils.js file isn't loaded yet, so the used function isn't defined, causing an error and falling back to following the href of the link (which loads VE, but does so by loading a new page).