fix some issues with QEAmount use

- always cast amount_sat and amount_msat to int within QEAmount to avoid conversion issues
  on the Qt/python boundary
- lightningBalance/lightningCanSend/lightningCanReceive were returning a floating QEAMount instance, leading to a crash

electrum/gui/qml/qetypes.py

@@ -17,16 +17,16 @@ class QEAmount(QObject):
 
     def __init__(self, *, amount_sat: int = 0, amount_msat: int = 0, is_max: bool = False, from_invoice = None, parent=None):
         super().__init__(parent)
-        self._amount_sat = amount_sat
-        self._amount_msat = amount_msat
+        self._amount_sat = int(amount_sat) if amount_sat is not None else None
+        self._amount_msat = int(amount_msat) if amount_msat is not None else None
         self._is_max = is_max
         if from_invoice:
             inv_amt = from_invoice.get_amount_msat()
             if inv_amt == '!':
                 self._is_max = True
             elif inv_amt is not None:
-                self._amount_msat = inv_amt
-                self._amount_sat = from_invoice.get_amount_sat()
+                self._amount_msat = int(inv_amt)
+                self._amount_sat = int(from_invoice.get_amount_sat())
 
     valueChanged = pyqtSignal()
 

electrum/gui/qml/qewallet.py

@@ -306,22 +306,25 @@ class QEWallet(QObject):
     @pyqtProperty(QEAmount, notify=balanceChanged)
     def lightningBalance(self):
         if not self.isLightning:
-            return QEAmount()
-        self._lightningbalance = QEAmount(amount_sat=int(self.wallet.lnworker.get_balance()))
+            self._lightningbalance = QEAmount()
+        else:
+            self._lightningbalance = QEAmount(amount_sat=int(self.wallet.lnworker.get_balance()))
         return self._lightningbalance
 
     @pyqtProperty(QEAmount, notify=balanceChanged)
     def lightningCanSend(self):
         if not self.isLightning:
-            return QEAmount()
-        self._lightningcansend = QEAmount(amount_sat=int(self.wallet.lnworker.num_sats_can_send()))
+            self._lightningcansend = QEAmount()
+        else:
+            self._lightningcansend = QEAmount(amount_sat=int(self.wallet.lnworker.num_sats_can_send()))
         return self._lightningcansend
 
     @pyqtProperty(QEAmount, notify=balanceChanged)
     def lightningCanReceive(self):
         if not self.isLightning:
-            return QEAmount()
-        self._lightningcanreceive = QEAmount(amount_sat=int(self.wallet.lnworker.num_sats_can_receive()))
+            self._lightningcanreceive = QEAmount()
+        else:
+            self._lightningcanreceive = QEAmount(amount_sat=int(self.wallet.lnworker.num_sats_can_receive()))
         return self._lightningcanreceive
 
     @pyqtSlot()