[SQUASH] Fix informatives for each pair not being created because dataprovider was not available.

Fix not being able to have informative dataframe of a pair in whitelist.

freqtrade/optimize/backtesting.py

@@ -154,11 +154,12 @@ class Backtesting:
         self.strategy: IStrategy = strategy
         strategy.dp = self.dataprovider
         # Attach Wallets to Strategy baseclass
-        IStrategy.wallets = self.wallets
+        strategy.wallets = self.wallets
         # Set stoploss_on_exchange to false for backtesting,
         # since a "perfect" stoploss-sell is assumed anyway
         # And the regular "stoploss" function would not apply to that case
         self.strategy.order_types['stoploss_on_exchange'] = False
+        strategy._initialize()
 
     def _load_protections(self, strategy: IStrategy):
         if self.config.get('enable_protections', False):