Fix NullPointerException when visitListItem encounters a non-paragraph first child.
#1409
| Job | Run time |
|---|---|
| 1m 45s | |
| 1m 54s | |
| 1m 13s | |
| 2m 48s | |
| 2m 19s | |
| 1m 23s | |
| 2m 13s | |
| 1m 15s | |
| -1s | |
| 14m 49s |