compiler warning on osx

git head on osx (xcode 8), gives:

../../ntpdig/main.c:1709:28: warning: variable 'latest' is uninitialized when used here [-Wuninitialized]
        us_latest = tspec_to_tval(latest);
                                  ^~~~~~
../../ntpdig/main.c:1700:2: note: variable 'latest' is declared here
        struct timespec                 latest;
        ^
1 warning generated.

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