count distinct sequence_file ids

fixes issue with sequence_file count for sample_sets accessible to
multiple groups

server/web2py/applications/vidjil/models/sample_set_list.py

@@ -66,7 +66,7 @@ class SampleSetList():
             s_table.info.with_alias('info'),
             db.auth_user.last_name.with_alias('creator'),
             db.sequence_file.size_file.sum().with_alias('size'),
-            db.sequence_file.id.count().with_alias('file_count'),
+            db.sequence_file.id.count(distinct=True).with_alias('file_count'),
             db.anon_permission.name.with_alias('has_permission'),
             group_configs,
             group_config_ids,