qt: add missing case for on-chain fallback for BIP21 payment identfier containing lightning invoice

electrum/gui/qt/send_tab.py

@@ -698,6 +698,8 @@ class SendTab(QWidget, MessageBoxMixin, Logger):
                 num_sats_can_send = int(lnworker.num_sats_can_send())
                 msg += '\n' + _('Your channels can send {}.').format(self.format_amount(num_sats_can_send) + ' ' + self.base_unit())
             if not choices:
+                if not can_pay_onchain:
+                    msg += '\n' + _('Also, you have insufficient funds to pay on-chain.')
                 self.window.show_error(msg)
                 return
             r = self.window.query_choice(msg, choices)

electrum/payment_identifier.py

@@ -173,6 +173,8 @@ class PaymentIdentifier(Logger):
             return True
         if self._type in [PaymentIdentifierType.LNURLP, PaymentIdentifierType.BOLT11, PaymentIdentifierType.LNADDR]:
             return bool(self.bolt11) and bool(self.bolt11.get_address())
+        if self._type == PaymentIdentifierType.BIP21:
+            return bool(self.bip21.get('address', None)) or (bool(self.bolt11) and bool(self.bolt11.get_address()))
 
     def is_multiline(self):
         return bool(self.multiline_outputs)