Fix seg fault in s_time

Passing a negative value for the "-time" option to s_time results in a seg
fault. This commit fixes it so that time has to be greater than 0.
Reviewed-by: NAndy Polyakov <appro@openssl.org>

apps/s_time.c

@@ -283,6 +283,10 @@ static int parseArgs(int argc, char **argv)
             if (--argc < 1)
                 goto bad;
             maxTime = atoi(*(++argv));
+            if(maxTime <= 0) {
+                BIO_printf(bio_err, "time must be > 0\n");
+                badop = 1;
+            }
         } else {
             BIO_printf(bio_err, "unknown option %s\n", *argv);
             badop = 1;
@@ -527,7 +531,8 @@ int MAIN(int argc, char **argv)
          nConn, totalTime, ((double)nConn / totalTime), bytes_read);
     printf
         ("%d connections in %ld real seconds, %ld bytes read per connection\n",
-         nConn, (long)time(NULL) - finishtime + maxTime, bytes_read / nConn);
+         nConn, (long)time(NULL) - finishtime + maxTime,
+         bytes_read / (nConn?nConn:1));
 
     ret = 0;
  end: