FIX: inbound link when the only slug available (PR #8457)

Problem mentioned in meta

When there is an internal link without ID, only slug, we should still try to create reflection link.


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oh the index is on topic_slug is not null so this can trigger a table scan… instead double query is probably correct here

topic = Topic.find_by(id: topic_id)
if !topica && topic_slug
    topic = Topic.find_by(slug: topic_slug)

Yeah looks good to me… merge at will.