[OSIS-3527] fix AttributeError entities for excel proposal
[OSIS-3527] fix AttributeError entities for excel proposal

	modified:   base/views/learning_units/search/common.py

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