hs-v3: Assertion onion_pk failed in introduce1_set_encrypted_onion_key

From #tor on IRC, someone using Tor Browser hit this. I would bet anything that #27471 (moved) is also related in some way.

9/18/18, 17:42:12.963 [ERR] tor_assertion_failed_(): Bug: src/or/hs_cell.c:256: introduce1_set_encrypted_onion_key: Assertion onion_pk failed; aborting. (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.964 [ERR] Bug: Assertion onion_pk failed in introduce1_set_encrypted_onion_key at src/or/hs_cell.c:256. Stack trace: (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.965 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(log_backtrace+0x44) [0x5601001fa314] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.965 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(tor_assertion_failed_+0x8d) [0x56010021587d] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.965 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(hs_cell_build_introduce1+0x457) [0x5601001f5ee7] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.965 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(hs_circ_send_introduce1+0x296) [0x5601001d4596] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.965 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(hs_client_send_introduce1+0x159) [0x5601001d7299] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.965 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(connection_ap_handshake_attach_circuit+0x860) [0x56010015f210] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.966 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(connection_ap_attach_pending+0x1a8) [0x560100180308] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.966 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(circuit_send_next_onion_skin+0x372) [0x560100149762] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.967 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(+0x7be34) [0x5601000ece34] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.967 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(circuit_receive_relay_cell+0x329) [0x5601000eee59] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.967 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(command_process_cell+0x180) [0x56010015ff40] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.967 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(channel_tls_handle_cell+0x32b) [0x5601001401cb] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(+0x115507) [0x560100186507] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(+0x10c01e) [0x56010017d01e] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(+0x52d31) [0x5601000c3d31] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     ./TorBrowser/Tor/libevent-2.1.so.6(+0x2214a) [0x7f70d3fa714a] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     ./TorBrowser/Tor/libevent-2.1.so.6(event_base_loop+0x55f) [0x7f70d3fa7c6f] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(do_main_loop+0x26c) [0x5601000c4d4c] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(tor_run_main+0x275) [0x5601000c6365] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(tor_main+0x3a) [0x5601000bf91a] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(main+0x19) [0x5601000bf669] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf1) [0x7f70d31532e1] (on Tor 0.3.3.9 45028085ea188baf) 
9/18/18, 17:42:12.968 [ERR] Bug:     /home/winston/tor-browser_en-US/Browser/TorBrowser/Tor/tor(+0x4e6b9) [0x5601000bf6b9] (on Tor 0.3.3.9 45028085ea188baf)