I'm seeing minor errors in the console log -
Amir merged in the flat file import extension code yesterday afternoon. Are you seeing this error after running a full build (yarn and yarn run watch) since pulling from master?
I get a bunch of other errors now. Though the original one is gone.
Only the first error and the one about dark_icon.svg look relevant to importer there, the rest I think we've seen before. Does the extension work now regardless of the errors?
Closing issue, please reopen if the issue wasn't resolved.