qml: fix display of negative millisat amounts in qefx.py for historic amounts too

electrum/gui/qml/qefx.py

@@ -118,7 +118,7 @@ class QEFX(QObject, QtEventListener):
     @pyqtSlot(QEAmount, str, bool, result=str)
     def fiatValueHistoric(self, satoshis, timestamp, plain=True):
         if isinstance(satoshis, QEAmount):
-            satoshis = satoshis.msatsInt / 1000 if satoshis.msatsInt > 0 else satoshis.satsInt
+            satoshis = satoshis.msatsInt / 1000 if satoshis.msatsInt != 0 else satoshis.satsInt
         else:
             try:
                 sd = Decimal(satoshis)