You are wrongly logged out from "Firefox Notes" after reopening the sidebar if two notes were previously deleted

[Softvision-MariusComan]

[Affected versions]:

• Firefox 59.0.2 and above

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a Firefox profile with the latest version of the "Firefox Notes" add-on (4.0.0 Beta 3) installed.
• You are logged into "Firefox Notes".
• Have minimum two notes in the sidebar.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites.
2. Click on a note and press the options menu button from the right side of the title.
3. Select the "Delete Note" option.
4. Repeat steps 2 and 3.
5. Close and reopen the sidebar.
6. Observe the bottom toolbar.

[Expected result]:

• The "Synced(hour) message is displayed.

[Actual result]:

• You are logged out and the "Sign in to Sync" message is displayed..

[Notes]:

• The issue is reproducible if you switch the sidebar or if you restart the browser.
• Attached a screen recording of the issue:
  

[sebastienbarbier]

Currently working on this one, similar to #802

[sebastienbarbier]

Playing with delete feature, I received few times 500 from server (Kinto team actually reported it on github : Kinto/kinto#1557). However could not reproduce on purpose.
One other issue I received was the following error message:

TypeError: resolution is undefined
Stack trace:
syncKinto/</<@moz-extension://79a6ec10-37db-ae4f-9f84-fbf82f43c79f/sync.js:220:15
syncKinto/<@moz-extension://79a6ec10-37db-ae4f-9f84-fbf82f43c79f/sync.js:192:28

So hopefully ... handling or fixing those two might solve this problem.

[Softvision-MariusComan]

This issue is no longer reproducible with the latest version of the "Firefox Notes" add-on (4.0.0 Beta 5 build) installed, on the latest Firefox release and Nightly. Verified on Windows 10 x64, Mac 10.12 and Ubuntu 14.04 x64.