Prevent v_oc to be negative in _lambertw
#1159
| Job | Run time |
|---|---|
| 2m 48s | |
| 1m 28s | |
| 3m 5s | |
| 1m 8s | |
| 2m 49s | |
| 1m 11s | |
| 2m 48s | |
| 1m 25s | |
| 2m 47s | |
| 1m 12s | |
| 1m 6s | |
| 2m 5s | |
| 2m 6s | |
| 2m 4s | |
| 1m 56s | |
| 5m 37s | |
| 8m 11s | |
| 4m 26s | |
| 4m 30s | |
| 6m 11s | |
| 1m 8s | |
| 1h 0m 1s |