Re-Open tasks list when needed.

Indeed, before this patch we were using the reference instead of
"reopening" the task list each time we needed to access it.
Without this patch, all other usage of the task attribute will
break.

dump/src/reader/v5/mod.rs

@@ -142,7 +142,7 @@ impl V5Reader {
             V5IndexReader::new(
                 index.uid.clone(),
                 &self.dump.path().join("indexes").join(index.index_meta.uuid.to_string()),
-                BufReader::new(self.tasks.get_ref().try_clone().unwrap()),
+                BufReader::new(File::open(&self.dump.path().join("updates").join("data.jsonl")).unwrap()),
             )
         }))
     }