Mate , It's related to the TWRP you have flashed Which was provided by ShevT ( actually , I don't recommend switching into the other TWRPs which were provided by other developers .. they are laggy and unstable

) all you need to do is to do the following process :
1 - extract your ROM zip
2 - go inside your ROMs extracts and go to this address : /META-INF/com/google/android
3 - There you need to open "updater-script" with " WordPad " ( if you open it with notepad , you'll face a mess so don't open it with notepad )
4 - You can see that there in the first line , there is "assert(...." you need to choose from "assert" to the first ";" and delete it

5 - save the file and exit !!
6 - Compress the ROM's folders and flash it :laugh:
Good luck
With Best Wishes
Hitman1376