Single characters are not saved/synced when they are typed in a different window if the sidebar was previously empty

[Softvision-MariusComan]

[Affected versions]:

• Firefox 57.0.4 and up

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a Firefox profile with the latest version of the "Firefox Notes" add-on (2.2.0dev custom build from 01.16.2018) installed.
• Do not have content in the "Firefox Notes" sidebar.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites.
2. Press "Ctrl+N" and focus the sidebar in the newly opened window .
3. Insert a character and observe the message displayed in the bottom of the toolbar.
4. Insert a second character and observe the message displayed in the bottom of the toolbar.

[Expected result]:
Step 3: The "Saving changes..." message is displayed.
Step 4: The "Saving changes..." message is displayed.

[Actual result]:
Step 3: The "Saved at hour" message is displayed.
Step 4: The "Saving changes..." message is displayed.

[Notes]:

• The issue is reproducible when you are logged into the "Firefox Notes".
• The issue is reproducible with the TxP version of "Firefox Notes".
• Attached a screen recording of the issue:
  

[Softvision-MariusComan]

The issue is no longer reproducible with the latest version of the "Firefox Notes" add-on (2.2.0dev custom build from 01.25.2018) installed, on the latest Firefox release and Nightly.