Breadcrumb bar initially shows the item selected from dropdown, but not after navigating to child item

**Operating System**: Windows

**DocFX Version Used**: 2.57.2

**Template used**: default

**Steps to Reproduce**:

1. Expand [docfx-dropdown-breadcrumb.zip](https://github.com/dotnet/docfx/files/6523567/docfx-dropdown-breadcrumb.zip)
2. `cd docfx-dropdown-breadcrumb`
3. `docfx build --serve`
4. Browse to
5. Click "Mobile apps" in the top navigation bar.
The dropdown list opens and contains items "App A" and "App B".
6. Click "App A" in the dropdown list.
This navigates to . The breadcrumb bar says "App A". The table of contents shows that there is only one child item, "Credits".
7. Click "Credits" in the table of contents.
This navigates to .

**Expected Behavior**:

The breadcrumb bar shows "App A" and "Credits".

**Actual Behavior**:

The breadcrumb bar shows only "Credits".