Tabs remain in condensed mode if sidebar is hovered at browser start

[SoftVision-PaulOiegas]

[Affected versions]:

• Firefox 52.0 and above
• Tab Center 1.31.0 (release version)
• Tab Center custom repository build

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Tab Center was already installed on a new Firefox profile from Test Pilot or from custom repository build.
• In about:preferences#general page, set the option "Show my windows and tabs from last time".

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites.
2. Open a couple of web pages in different tabs (without passing to condensed view).
3. Remember the sidebar position on the screen and restart / close the browser.
4. Restart the browser and hover the area where the sidebar is positioned.
5. Observe the sidebar behavior.

[Expected result]:
The sidebar displays the previously opened web pages with the page preview.

[Actual result]:
The sidebar wrongly displays the previously opened web pages in condensed view.

[Notes]:

• It seams that when Tab Center is initialized at browser start, the tabs are shortly displayed in condensed view first. And if the sidebar is hovered they remain like that until you hover away.
• See attached screen recording of the issue: https://goo.gl/opmDH9.