fix price check and transaction editor to handle nulls

app/activities/PriceCheck.py

@@ -152,7 +152,7 @@ class PriceCheck(FocusWidget):
             self.rating.update_rating(None, None, None, unit)
             return
 
-        df = self.query_manager.get_historic_prices_data(unit, sort=sort, product=product, organic=organic)
+        df = self.query_manager.get_historic_prices_data(unit, sort=sort, product=product, organic=organic).dropna()
         if df.empty:
             self.text_fields['dbview'].set_text('')
             self.rating.update_rating(None, None, None, unit)

app/activities/TransactionEditor.py

@@ -174,7 +174,7 @@ class TransactionEditor(FocusWidget):
             self.rating.update_rating(None, None, None, unit)
             return
 
-        df = self.query_manager.get_historic_prices_data(unit, product=product, organic=organic, sort='ts')
+        df = self.query_manager.get_historic_prices_data(unit, product=product, organic=organic, sort='ts').dropna()
         if df.empty:
             self.rating.update_rating(None, None, None, unit)
             return