Fix calls to update_fee

Fees should be recalculated when send_from changes.
Fees should be recalculated when editing fee preference, but
only save to storage when leaving the fee per kb widget.
No need to emit a textEdited signal; the widget does that already
(with the effect that we used to call update_fee() twice).

gui/qt/paytoedit.py

@@ -135,8 +135,6 @@ class PayToEdit(ScanQRTextEdit):
         else:
             self.amount_edit.setText("")
 
-        self.amount_edit.textEdited.emit("")
-
         if total or len(lines)>1:
             self.lock_amount()
         else: