Minor inconsistency when using prod module in centifuge

[ejg]

When trying to use a production module in a centrifuge with the recipe set to 'nuclear fuel' one receives the message:

"Productivity modules are only usable on intermediate products" while nuclear fuel is listed as intermediate product (of course it isn't since nothing uses it but then it is wrongly listed). This behaviour is confusing in my opinion. (don't start the discussion about Kovarex Enrichment again)