I got that too. You have to be careful when installing to your hard drive. The install will reboot several times. Once it rebooted when it said 30 minutes remaining. You need to make sure you are pressing F12 and choosing the USB to continue the install. If it boots from the hard drive, it won't be ready yet and will fail. Hard drive seemed to be the default on my BIOS boot menu, not USB. You could use Dell's BIOS Boot Sequence menu and move the USB to the top.
So press F12 at each reboot and choose the USB disk to boot from. This will bring you to the Clover Bootloader. Choose the option "Boot macOS Install from [HDD partition name]. Don't choose "Boot macOS install from [USB partition name]" anymore. You only do that on first boot with USB. At about the 3rd reboot, Clover will present more choices. Choose "Boot FileVault Preloader from Preload". This must be new to Mojave 10.14.3/5.
In summary press F12 and boot with USB until you have gone through all the setup (choosing language, iCloud, password, etc) and installed Clover, kexts into Library/Extensions and updated the plist.config on your hard drive's EFI partition. Follow post 1 instructions carefully. I also find
Rehabman's guide for installing Clover for laptops useful for this whole process, start to finish.