The facet summary block is never truly empty, if there are no active filters then the block itself will still be outputted since the renderable array is always filled in the DefaultFacetsSummaryManager.
The issue arises in DefaultFacetsSummaryManager::build, where $build is set with the theme callback and '#items' is set with the results or an empty array.
Only initialise build with the theme data if there are actually results. All processors check for the existence of $build['#items'] already so they will remain working.
#2951763: Show count processor should always build when enabled. →
Needs review
2.0
Facet summary
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
The problem is also present in version 2.x of the module.
This adapted patch fixes the problem for me, by just not adding Javascript if the block is empty.