Keep rebooting if no WAN connection

I have WT3020 travel router and install lede 17.04
I use this router for NAS and no need any internet
However I found out router keep rebooting if no WAN connection
Anyway to prevent this?

did you installed some watchdog or another package someting ?

sorry, false alarm
after observation, it appears the router rebooted because out of memory, not due to no wan connection
i make swap in router and now seems to be stable