qt rbf_dialog: set output_value properly

to also show high fee warnings for bump_fee/dscancel flows

fixes https://github.com/spesmilo/electrum/issues/9273

electrum/gui/qt/confirm_tx_dialog.py

@@ -61,7 +61,7 @@ class TxEditor(WindowModalDialog):
     def __init__(self, *, title='',
                  window: 'ElectrumWindow',
                  make_tx,
-                 output_value: Union[int, str] = None,
+                 output_value: Union[int, str],
                  allow_preview=True):
 
         WindowModalDialog.__init__(self, window, title=title)

electrum/gui/qt/rbf_dialog.py

@@ -40,11 +40,17 @@ class _BaseRBFDialog(TxEditor):
         self.old_tx_size = tx.estimated_size()
         self.old_fee_rate = old_fee_rate = self.old_fee / self.old_tx_size  # sat/vbyte
 
+        output_value = sum([txo.value for txo in tx.outputs() if not txo.is_mine])
+        if output_value == 0:
+            output_value = tx.output_value()
+
         TxEditor.__init__(
             self,
             window=main_window,
             title=title,
-            make_tx=self.rbf_func)
+            make_tx=self.rbf_func,
+            output_value=output_value,
+        )
 
         self.fee_e.setFrozen(True)  # disallow setting absolute fee for now, as wallet.bump_fee can only target feerate
         new_fee_rate = self.old_fee_rate + max(1, self.old_fee_rate // 20)