This is an eggcorn for the much more common idiom trackless wilderness.
Like all the best eggcorns, though, it’s a very plausible reinterpretation, as Martin Beckett’s answer describes, since tracts can mean divisions of land, esp. into properties, which (like tracks) are something a wilderness would typically lack.
The reinterpretation seems to have arise quite often, as Google Books and ngrams show, going back at least to the early eighteenth century; for instance:
The difficulty of placing these correctly in a tractless wilderness, which has never been accurately measured, will at once plead both his excuse and mine.
from an 1811 bible commentary mapping the travels of the Israelites.