0a5d18634c
See discussion at https://github.com/spesmilo/electrum/commit/583089d57b517ab001721cfc9e4d883f3d4c4f7c#r104678577 CoinGecko for PLN gives "None" str as rate (instead of null) for two months mid-2014: ``` 2.29 | D | exchange_rate.CoinGecko | found corrupted historical_rate: rate='None'. for ccy='PLN' at 2014-05-10 ``` Thanks to @lukasz1992 for reporting.