Merge pull request #10572 from f321x/fix_coingecko

exchange rate: fix coingecko api

Author: SomberNight

electrum/exchange_rate.py

@@ -447,7 +447,7 @@ class CoinGecko(ExchangeBase):
     async def get_rates(self, ccy):
         json = await self.get_json('api.coingecko.com', '/api/v3/exchange_rates')
         return dict([(ccy.upper(), to_decimal(d['value']))
-                     for ccy, d in json['rates'].items()])
+                     for ccy, d in json['rates'].items() if d.get('value') is not None])
 
     def history_ccys(self):
         # CoinGecko seems to have historical data for all ccys it supports