Update src/hiero_sdk_python/transaction/transaction_record.py

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Signed-off-by: MontyPokemon <59332150+MonaaEid@users.noreply.github.com>

Author: MonaaEid

src/hiero_sdk_python/transaction/transaction_record.py

@@ -245,7 +245,7 @@ def _from_proto(
 
         return cls(
             transaction_id=tx_id,
-            transaction_hash=proto.transactionHash,
+            transaction_hash=proto.transactionHash or None,
             transaction_memo=proto.memo,
             transaction_fee=proto.transactionFee,
             receipt=TransactionReceipt._from_proto(proto.receipt, tx_id),