fix https://github.com/acmesh-official/acme.sh/issues/992

Dockerfile

@@ -26,7 +26,7 @@ COPY ./ /install_acme.sh/
 RUN cd /install_acme.sh && ([ -f /install_acme.sh/acme.sh ] && /install_acme.sh/acme.sh --install || curl https://get.acme.sh | sh) && rm -rf /install_acme.sh/
 
 
-RUN ln -s  /root/.acme.sh/acme.sh  /usr/local/bin/acme.sh && crontab -l | grep acme.sh | sed 's#> /dev/null##' | crontab -
+RUN ln -s /root/.acme.sh/acme.sh /usr/local/bin/acme.sh && crontab -l | grep acme.sh | sed 's#> /dev/null#> /proc/1/fd/1 2>/proc/1/fd/2#' | crontab -
 
 RUN for verb in help \
   version \