Don't fail contract size repopulation if pair is no longer available

freqtrade/exchange/exchange.py

@@ -412,9 +412,11 @@ class Exchange:
 
     def get_contract_size(self, pair: str) -> float:
         if self.trading_mode == TradingMode.FUTURES:
-            market = self.markets[pair]
+            market = self.markets.get(pair, {})
             contract_size: float = 1.0
-            if market['contractSize'] is not None:
+            if not market:
+                return None
+            if market.get('contractSize') is not None:
                 # ccxt has contractSize in markets as string
                 contract_size = float(market['contractSize'])
             return contract_size

tests/exchange/test_exchange.py

@@ -4341,9 +4341,10 @@ def test__fetch_and_calculate_funding_fees_datetime_called(
     ('XLTCUSDT', 1, 'spot'),
     ('LTC/USD', 1, 'futures'),
     ('XLTCUSDT', 0.01, 'futures'),
-    ('ETH/USDT:USDT', 10, 'futures')
+    ('ETH/USDT:USDT', 10, 'futures'),
+    ('TORN/USDT:USDT', None, 'futures'),  # Don't fail for unavailable pairs.
 ])
-def est__get_contract_size(mocker, default_conf, pair, expected_size, trading_mode):
+def test__get_contract_size(mocker, default_conf, pair, expected_size, trading_mode):
     api_mock = MagicMock()
     default_conf['trading_mode'] = trading_mode
     default_conf['margin_mode'] = 'isolated'