`downloadsRemaining` returns `null` when is of valid type `string`

[hacknug]

What does this implement/fix? Explain your changes.

This PR fixes an issue when downloadsRemaining is of type string instead of the expected one integer. It changes how we check for valid values for downloadsRemaining everywhere in the codebase, and applies the most minimal set of changes to ensure we're not nullifying valid strigified values.

Does this close any currently open issues?

Closes #937.

Any relevant logs, error output, GraphiQL screenshots, etc?

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Any other comments?

Let me know if there's any extra changes you'd like me to make.