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Looks like #425 broke this feature. I should have had some integration tests for it, I guess. This is also the "right" fix for #424 (which I believe was only an issue from the home page, correct, @jkeck?)

@jcoyne can you let me know how to reproduce #423 and I'll take a look. I played around with adding `blacklight_config.exhibit` and couldn't recreate the problem, but maybe it's occurring in a different context..