"Quick submit" feature prints errors in console when tabbing to submit button

Summary

When tabbing to the "submit" button in a form with "quick submit" enabled (the ⌘+Enter or Ctrl+Entershortcut), an error message is printed in the browser console and no tooltip is shown on the button.

Steps to reproduce

1. Navigate to the New Milestone page /-/milestones/new
2. Open up the browser console (F12 in Firefox/Chrome)
3. Enter a Title (so that the form is valid)
4. Tab through the form until the Create milestone button is focused

What is the current bug behavior?

An error is printed in the browser console:

Uncaught Error: TOOLTIP: Option "html" provided type "string" but expected type "boolean".

and no tooltip is shown on the button.

What is the expected correct behavior?

No errors are printed in the console and a tooltip is shown on the button that reads, "You can also press ⌘-Enter".

Output of checks

This bug happens on GitLab.com.