[time] an epoch timestamp should not have whitespace

src/lnav_util.cc

@@ -513,7 +513,9 @@ const char *date_time_scanner::scan(const char *time_dest,
                        this->dts_fmt_lock)) {
         *tm_out = this->dts_base_tm;
         tm_out->et_flags = 0;
-        if (time_dest[0] == '+') {
+        if (time_len > 1 &&
+            time_dest[0] == '+' &&
+            isdigit(time_dest[1])) {
             char time_cp[time_len + 1];
             int gmt_int, off;