wallet: (trivial) add asserts re args in bump_fee and friends

for clearer exceptions in case of bugs

related https://github.com/spesmilo/electrum/issues/8571

electrum/transaction.py

@@ -1858,6 +1858,7 @@ class PartialTransaction(Transaction):
 
     @classmethod
     def from_tx(cls, tx: Transaction) -> 'PartialTransaction':
+        assert tx
         res = cls()
         res._inputs = [PartialTxInput.from_txin(txin, strip_witness=True)
                        for txin in tx.inputs()]

electrum/wallet.py

@@ -2073,6 +2073,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
         note: it is the caller's responsibility to have already called tx.add_info_from_network().
               Without that, all txins must be ismine.
         """
+        assert tx
         if not isinstance(tx, PartialTransaction):
             tx = PartialTransaction.from_tx(tx)
         assert isinstance(tx, PartialTransaction)
@@ -2300,6 +2301,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
         return True
 
     def cpfp(self, tx: Transaction, fee: int) -> Optional[PartialTransaction]:
+        assert tx
         txid = tx.txid()
         for i, o in enumerate(tx.outputs()):
             address, value = o.address, o.value
@@ -2335,6 +2337,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
         note: it is the caller's responsibility to have already called tx.add_info_from_network().
               Without that, all txins must be ismine.
         """
+        assert tx
         if not isinstance(tx, PartialTransaction):
             tx = PartialTransaction.from_tx(tx)
         assert isinstance(tx, PartialTransaction)