Fix "Key error" problem in swap_empty_internships
Fix "Key error" problem in swap_empty_internships

uclouvain/osis_louvain,uclouvain/OSIS-Louvain,uclouvain/osis_louvain,uclouvain/osis_louvain,uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/osis