"Add Current Tab" button disabled, and incorrect context menu item appears, when navigating reading list link in a new browser window

[aecreations]

Read Next 1.1.7

Steps to repro:

1. Add a link to the reading list sidebar
2. With the sidebar still open, navigate to another page or website that isn't already linked in the reading list; don't add it to the reading list
3. Right-click on the link that was added in step 1, and choose the option to open the link in a new window

Results:

1. The "Add Current Tab" button is disabled.
2. In the context menu (either in the browser tab or in the page), the menu item for deleting the link appears, even though the current page isn't in the reading list.

The address bar button is unaffected.

Workaround:
Switch to another browser tab, then switch back to update the toolbar button and the context menu items.

[aecreations]

The same issue occurs when right-clicking on a link in the web page and opening it in a new browser tab, and that link was already saved to the reading list.

[aecreations]

Adding to reading list is also affected. If I add a web page in browser window A to the reading list, the "Add Current Tab" button in the sidebar is incorrectly disabled in browser window B that is displaying a web page that isn't in the reading list.

There is similar disabling logic on the "Add Current Tab" button when removing a reading list item.