fix: custom fee handling

Signed-off-by: exploreriii <133720349+exploreriii@users.noreply.github.com>

Author: exploreriii

src/hiero_sdk_python/tokens/token_create_transaction.py

@@ -453,7 +453,9 @@ def build_transaction_body(self) -> transaction_body_pb2.TransactionBody:
             token_create_body.pause_key.CopyFrom(pause_key_proto)
         if kyc_key_proto is not None:
             token_create_body.kycKey.CopyFrom(kyc_key_proto)
-        custom_fees=[fee._to_proto() for fee in self._token_params.custom_fees],
+        if self._token_params.custom_fees:
+            for fee in self._token_params.custom_fees:
+                token_create_body.custom_fees.append(fee._to_proto())
 
         # Build the base transaction body and attach the token creation details
         transaction_body: transaction_body_pb2.TransactionBody = self.build_base_transaction_body()