qml: invert, more strict check in determine_can_pay for invoice types,

also disable paste button while PI is being evaluated

electrum/gui/qml/components/SendDialog.qml

@@ -66,6 +66,7 @@ ElDialog {
             FlatButton {
                 Layout.fillWidth: true
                 Layout.preferredWidth: 1
+                enabled: !invoiceParser.busy
                 icon.source: '../../icons/copy_bw.png'
                 text: qsTr('Paste')
                 onClicked: {

electrum/gui/qml/qeinvoice.py

@@ -337,7 +337,7 @@ class QEInvoice(QObject, QtEventListener):
         self.canPay = False
         self.canSave = False
 
-        if self.invoiceType in [QEInvoice.Type.Invalid, QEInvoice.Type.LNURLPayRequest]:
+        if self.invoiceType not in [QEInvoice.Type.LightningInvoice, QEInvoice.Type.OnchainInvoice]:
             return
 
         if not self.amountOverride.isEmpty: