chore: fix init sequence to avoid risk of "unbound error"

Author: xmatthias

freqtrade/exchange/exchange.py

@@ -277,6 +277,11 @@ def __init__(
 
         logger.info(f'Using Exchange "{self.name}"')
         self.required_candle_call_count = 1
+        # Converts the interval provided in minutes in config to seconds
+        self.markets_refresh_interval: int = (
+            exchange_conf.get("markets_refresh_interval", 60) * 60 * 1000
+        )
+
         if validate:
             # Initial markets load
             self.reload_markets(True, load_leverage_tiers=False)
@@ -286,11 +291,6 @@ def __init__(
                 self._startup_candle_count, config.get("timeframe", "")
             )
 
-        # Converts the interval provided in minutes in config to seconds
-        self.markets_refresh_interval: int = (
-            exchange_conf.get("markets_refresh_interval", 60) * 60 * 1000
-        )
-
         if self.trading_mode != TradingMode.SPOT and load_leverage_tiers:
             self.fill_leverage_tiers()
         self.additional_exchange_init()