Possible pointer dereference

I'm playing with a static analyzer and it's giving out some real error
analyzing postgresql code base like the following one

src/backend/access/transam/commit_ts.c
return *ts != 0 // line 321
but a few line up (line 315) ts is checked for null, so either is not
needed to check for null or *ts can lead to a null pointer dereference.
Same happens a few line later lines 333 and 339

Regards
Gaetano