Odd behavior for breadcrumbs on exhibit item pages

[caaster]

Reported by @andrewjbtw.

The breadcrumbs on item pages behave oddly. I'm seeing them insert the last "browse category" I've viewed whether or not the item I'm viewing is actually in that browse category.

To reproduce:

1. Enter the URL for this page: https://exhibits.stanford.edu/maps-of-africa/catalog/fw646fg6941
2. See that the breadcrumb is only "Home / Map of the routes to the gold field"
3. Click on Browse and then choose "Caroline Batchelor Collection"
4. See that there's only one item in the collection and it's not "Map of the routes to the gold field"
5. Load this URL again: https://exhibits.stanford.edu/maps-of-africa/catalog/fw646fg6941
6. See that the breadcrumbs now include "Caroline Batchelor Collection"

I see this behavior in both Firefox and Chrome. It looks like the breadcrumbs will include whatever the last "Browse category" I've looked at each time I load an item's exhibit page.

[dnoneill]

Waiting until Blacklight 8 is installed. Think we can piggy back on projectblacklight/blacklight#2970 to solve this bug.