Simple fix for broken indirection docs

Currently generting the indirection docs fails because of the
resource/validator terminus, for which the autoloader returns nil.
Rather than quietly failing the whole docs build on this error, just
fail the docs for that particular terminus.

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This is the simplest fix, without delving into *why* the autoload isn't working.  Think of it as more of a band-aid than a fix, but hopefully not a problematic fix.