"Export as HTML..." tooltip is not displayed when hovering the "Export as HTML..." button

[SoftVision-EmilPasca]

[Notes]:

• After logging in to Firefox Notes, "Sync with ..." tooltip is wrongly displayed when hovering the "Export as HTML..." button.

[Affected versions]:

• Firefox 58.0.2 and up

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a Firefox profile with the latest "Firefox Notes" add-on version (3.0.0 installed from https://1228-91073350-gh.circle-artifacts.com/0/tmp/circle-artifacts.MicZiHM/firefox_notes-3.0.0.zip)

[Steps to reproduce]:

1. Open Firefox browser with the profile from prerequisites.
2. Hover the "Export as HTML..." button from the "Notes" three dots menu.
3. Observe the "Export as HTML..." tooltip.

[Expected result]:

• The "Export as HTML..." tooltip is displayed.

[Actual result]:

• The "Export as HTML..." tooltip is not displayed.

[Additonal Notes]:

• Here is a screen recording with this issue: