Default [Q] Navigation bar go missing after reboot to safe mode

I am using Omnimetal custom ROM. Just now I tried out rebooting the phone to safe mode. After rebooted to safe mode, I rebootted the phone again back to normal mode. However , I found out that my navigation bar and status bar go missing. I tried to swipe up or down, both navigation bar and status bar would not appear. Would like to know how can I fix it instead of reinstalling the custom Omnimetal ROM. Thanks.