This seems like a fun one, when you compare a list to a string you get this cool panic:

Query Failed - unknown error: unable to cast []interface {}{"DirectoryOfThisScript", "MakeRelativePathsInFlagsAbsolute", "FlagsForFile"} of type []interface {} to string

The query generating this is indeed incorrect, but the error message should be better.

  SELECT UAST_EXTRACT(UAST(f.blob_content, LANGUAGE(f.file_path, f.blob_content), '//Identifier'), 'Name') as names
  FROM   files AS f
  WHERE  names != ''

Replacing the condition with WHERE names IS NOT NULL will fix the error, but the message should be more clear.