Product Catalog uploads old non-functional variations

Hi there!

I have an enhancement request regarding a strange issue.

When generating the product catalog, we get errors from Facebook saying that we have some duplicate IDs. Upon closer inspection, it seems that these errors are generated by child variations of simple products! See the following excerpt from the feed xml (irrelevant elements removed):

<entry>
  <g:id>999000</g:id>
  <g:link>https://[redacted]/trendikas-ball-mason-jar-smuutipurk/</g:link>
  <g:checkout_url>https://[redacted]/trendikas-ball-mason-jar-smuutipurk/?variation_id=674&add-to-cart=207</g:checkout_url>
  <g:item_group_id>999000</g:item_group_id>
</entry>
[....]
<entry>
  <g:id>999000</g:id>
  <g:link>https://[redacted]/trendikas-ball-mason-jar-smuutipurk/</g:link>
  <g:checkout_url>https://[redacted]/trendikas-ball-mason-jar-smuutipurk/?add-to-cart=207</g:checkout_url>
</entry>

My best guess is that someone created these products as variable products a long time ago and then later they were changed to simple products, so the variations were not deleted. This would also explain why the g:item_group element is not added to the parent. I’m doing a manual database cleanup to resolve the problem right now. However, it would be great if you plugin could check if the variation parent is actually a variable product before adding it to the feed.

Thanks!