wallet: consider "future" coins as frozen by default

electrum/gui/qt/main_window.py

@@ -465,6 +465,8 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger, QtEventListener):
     def on_event_adb_set_future_tx(self, adb, txid):
         if adb == self.wallet.adb:
             self.history_model.refresh('set_future_tx')
+            self.utxo_list.refresh_all()  # for coin frozen status
+            self.update_status()  # frozen balance
 
     @qt_event_listener
     def on_event_verified(self, *args):

electrum/wallet.py

@@ -1966,6 +1966,9 @@ class Abstract_Wallet(ABC, Logger, EventListener):
         if frozen is not None:  # user has explicitly set the state
             return bool(frozen)
         # State not set. We implicitly mark certain coins as frozen:
+        tx_mined_status = self.adb.get_tx_height(utxo.prevout.txid.hex())
+        if tx_mined_status.height == TX_HEIGHT_FUTURE:
+            return True
         if self._is_coin_small_and_unconfirmed(utxo):
             return True
         return False