Thread:Extension talk:Scribunto/Difficulties in getting this extension to work/reply (5)

From the error you linked in step 3, it seems like you somehow got your wiki into a situation where one of the entries returned from $wgContLang->getFormattedNamespaces had a null name.

I have no idea how importing stuff in step 3 might have given you a broken namespace, nor how what you did in step 10 fixed it (unless you happened to create your "Backup" namespace with the same number as whatever the broken namespace was).