Sent text does not appear in the sidebar if it was sent to the sidebar from a different window and that sidebar is closed

[Softvision-MariusComan]

https://bugzilla.mozilla.org/show_bug.cgi?id=1470464

[Affected versions]:

• Firefox 61 and above

[Affected Platforms]:

• All Windows
• All Linux
• All Mac

[Prerequisites]:

• Have a new Firefox profile with the latest version of the "Firefox Notes" add-on (4.2.0dev custom built on 22.06.2018) installed.
• Have two windows opened.
• Have any website with text opened in both windows.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites and focus any window.
2. Select any text from the opened website.
3. Right click the selected text and click the "Add to Notes" option.
4. Close the sidebar and focus the other window.
5. Repeat steps 2 and 3.
6. Observe the behavior.

[Regression window]:
Last good revision: 3e60aeb17f19c7f62c72db721e380598e02f9f09
First bad revision: 2cbcfa64364bdf2f74e552f0d3e0cfafd7756ae6
Pushlog:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=3e60aeb17f19c7f62c72db721e380598e02f9f09&tochange=2cbcfa64364bdf2f74e552f0d3e0cfafd7756ae6

From the pushlog it seems that Bug 1444758 has caused this regression.

[Expected result]:

• A new note containing the text from step 5 is displayed.

[Actual result]:

• The sidebar flickers and the new note is not displayed.

[Notes]:

• The issue is not reproducible if you send the text to notes a second time.
• Attached a screen recording of the issue: