tryReadTBQueueDefault: fix bug when returning Nothing
#721
| Job | Run time |
|---|---|
| 10m 29s | |
| 22m 49s | |
| 14m 22s | |
| 10m 13s | |
| 9m 42s | |
| 15m 0s | |
| 10m 37s | |
| 11m 56s | |
| 13m 35s | |
| 11m 12s | |
| 10m 40s | |
| 13m 12s | |
| 10m 29s | |
| 10m 44s | |
| 10m 48s | |
| 9m 3s | |
| 11m 1s | |
| 17m 6s | |
| 3h 42m 58s |