Unpinning on empty hover can fail when actionsOrError is an empty array

[lguychard]

See https://sourcegraph.slack.com/archives/C07KZF47K/p1563370310155400?thread_ts=1563353869.150100&cid=C07KZF47K

I'm torn between fixing this in sourcegraph/sourcegraph, sourcegraph/codeintellify or both, but filing here as a starting point.