Fix:

$ ksh93
$ time
../src/cmd/ksh93/sh/xec.c:2171: failed assertion 'tb.tv_sec'
Abort trap (core dumped)
$ ksh93
$ times
../src/cmd/ksh93/sh/xec.c:2171: failed assertion 'tb.tv_sec'
Abort trap (core dumped)

PR: 239701
Suggested by: w.schwarzenfeld@utanet.at
MFH: 2019Q3