Failed chain freezer on Privnet

[txhsl]

System information

Geth version: 0.5.0-unstable
OS & Version: Linux
Commit hash : f20d5b7

Expected behaviour

We expect the v1.14.13 code from #487 to work well.

Actual behaviour

Ref #499 (comment).

Steps to reproduce the behaviour

1. Make geth;
2. Start up a local Privnet, e.g. the four-node one;
3. Check the log of node5.

Backtrace

INFO [09-26|18:11:40.555] Rebuilt trie database                    root=e9f7e9..bb34fc
INFO [09-26|18:11:40.556] Rebuilding state snapshot
INFO [09-26|18:11:40.558] Committed new head block                 number=1 hash=3c8e71..ca5f41
INFO [09-26|18:11:40.568] Resuming state snapshot generation       root=e9f7e9..bb34fc accounts=0          slots=0             storage=0.00B    dangling=0 elapsed=4.975ms
WARN [09-26|18:11:40.655] Inserted known block                     number=3 hash=6328b2..17b21e uncles=0 txs=0 gas=0 root=e9f7e9..bb34fc
WARN [09-26|18:11:40.659] Inserted known block                     number=4 hash=f61a81..1966b0 uncles=0 txs=0 gas=0 root=e9f7e9..bb34fc
WARN [09-26|18:11:40.662] Inserted known block                     number=5 hash=c1472f..9a9c26 uncles=0 txs=0 gas=0 root=e9f7e9..bb34fc
WARN [09-26|18:11:40.669] Inserted known block                     number=6 hash=0f0c5a..7faac9 uncles=0 txs=0 gas=0 root=e9f7e9..bb34fc
WARN [09-26|18:11:40.679] Inserted known block                     number=7 hash=6e5248..a9a351 uncles=0 txs=0 gas=0 root=e9f7e9..bb34fc
WARN [09-26|18:11:40.691] Inserted known block                     number=8 hash=097928..ebbcbb uncles=0 txs=0 gas=0 root=e9f7e9..bb34fc
WARN [09-26|18:11:40.701] Inserted known block                     number=9 hash=5ac134..5929d9 uncles=0 txs=0 gas=0 root=e9f7e9..bb34fc
WARN [09-26|18:11:40.741] Inserted known block                     number=11 hash=9491e3..aedcf4 uncles=0 txs=0 gas=0 root=8ffa12..1b19db
INFO [09-26|18:11:40.745] Syncing: chain download in progress      synced=1100.00% chain=18.00B headers=11@6.00B bodies=11@6.00B receipts=11@6.00B eta=-5m59.007s
......
INFO [09-26|18:12:03.719] Imported new chain segment               number=71 hash=7a4e2d..4234be blocks=1  txs=0  mgas=0.000  elapsed=72.098ms  mgasps=0.000  snapdiffs=161.26KiB triediffs=957.28KiB triedirty=0.00B
ERROR[09-26|18:12:15.304] Error in block freeze operation          err="block receipts missing, can't freeze block 1"
INFO [09-26|18:12:30.405] Imported new chain segment               number=72 hash=320ab4..e5867a blocks=1  txs=7  mgas=19.666 elapsed=5.684s    mgasps=3.460  snapdiffs=199.54KiB triediffs=1.21MiB   triedirty=0.00B
......

This should be fixed in #496, or in another separated PR.