"Sorry... that page seems to be missing!" is a result when user clicks on TextMesh Pro Settings help icon

Issue: The textMesh Pro Settings window has a help icon, which should open documentation. In this case, it is not working.

Steps:

1. Create a project;
2. Go to "Edit" -> "Project Settings";
3. Find "TextMesh Pro"
4. Click "Import TPM Essentials";
5. Verify, that below the "TextMesh Pro" you get the "Settings" item;
6. Select it;
7. Click the help () icon.

Actual Result: "Sorry... that page seems to be missing!". A screenshot is added below in the "Attachments" section.

Expected Result: The documentation page should be opened.

Reproducible with:  6000.0.7f1