docker: guard auto-pull cronjob write, don't chmod a missing file

docker_setup_auto_pull_cronjob ran 'sudo chmod 600' on the cron file
unconditionally, even when the preceding 'sudo tee' failed to create it —
producing 'chmod: cannot access /etc/cron.d/armbian-docker-pull: No such
file or directory'. The wrapper-script write just above already guards its
tee and bails gracefully; the cron-file write did not.

Guard the cron tee the same way: on failure, warn and return (best-effort,
the feature is opt-in via ARMBIAN_DOCKER_AUTO_PULL), and only chmod when
the file was actually created.

Signed-off-by: Igor Pecovnik <igor@armbian.com>

Author: igorpecovnik

lib/functions/host/docker.sh

@@ -905,10 +905,18 @@ function docker_setup_auto_pull_cronjob() {
 		fi
 		sudo chmod +x "${wrapper_script}" || true
 
-		# Create/update cron file
+		# Create/update cron file. Guard the write like the wrapper script above:
+		# if the tee fails (sudo refused, /etc read-only, cron not really
+		# present, ...) we must NOT go on to chmod a file that was never
+		# created — that is what printed the confusing
+		# "chmod: cannot access '${cron_file}': No such file or directory".
+		# Treat it as best-effort and bail gracefully, same as the wrapper path.
 		display_alert "Creating/updating Docker auto-pull cronjob" "${cron_file}" "info"
-		echo "${cron_content}" | sudo tee "${cron_file}" > /dev/null
-		sudo chmod 600 "${cron_file}"
+		if ! echo "${cron_content}" | sudo tee "${cron_file}" > /dev/null 2>&1; then
+			display_alert "Docker auto-pull" "failed to create cronjob ${cron_file} (sudo/permissions?)" "warn"
+			return 0
+		fi
+		sudo chmod 600 "${cron_file}" || true
 
 		# Store hash for next time
 		sudo mkdir -p "$(dirname "${hash_file}")"