Added some bigfixes for sell_tag

freqtrade/strategy/interface.py

@@ -549,7 +549,7 @@ class IStrategy(ABC, HyperStrategyMixin):
         """
         if not isinstance(dataframe, DataFrame) or dataframe.empty:
             logger.warning(f'Empty candle (OHLCV) data for pair {pair}')
-            return False, False, None
+            return False, False, None, None
 
         latest_date = dataframe['date'].max()
         latest = dataframe.loc[dataframe['date'] == latest_date].iloc[-1]
@@ -564,7 +564,7 @@ class IStrategy(ABC, HyperStrategyMixin):
                 'Outdated history for pair %s. Last tick is %s minutes old',
                 pair, int((arrow.utcnow() - latest_date).total_seconds() // 60)
             )
-            return False, False, None
+            return False, False, None, None
 
         buy = latest[SignalType.BUY.value] == 1