Why does roflcopter have an empty protocol line in the consensus?

r roflcopter Qcrc8IhWf84BI34AQRKJU5q7EpU 2017-09-24 03:25:06 159.203.10.141 443 80
m EDFeSxWDaRrY9S2ZROrxpABlrFPqnJQ7IbYXpEdkQao
s Fast Guard HSDir Running Stable V2Dir Valid
v Tor 0.2.9.11
pr 
w Bandwidth=7110

The descriptor looks reasonably normal. There is no Sybil on that IP address. https://atlas.torproject.org/#details/41CADCF088567FCE01237E00411289539ABB1295

It is blank in all the votes too. It's blank in the vanilla-flavored consensus too.

What would cause the "pr" line to be left blank?

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