wallet2: guard against bad outputs in import_outputs

also some minor speedup

src/wallet/wallet2.cpp

@@ -9830,18 +9830,20 @@ size_t wallet2::import_outputs(const std::vector<tools::wallet2::transfer_detail
     crypto::public_key tx_pub_key = get_tx_pub_key_from_received_outs(td);
     const std::vector<crypto::public_key> additional_tx_pub_keys = get_additional_tx_pub_keys_from_extra(td.m_tx);
 
+    THROW_WALLET_EXCEPTION_IF(td.m_tx.vout[td.m_internal_output_index].target.type() != typeid(cryptonote::txout_to_key),
+        error::wallet_internal_error, "Unsupported output type");
     const crypto::public_key& out_key = boost::get<cryptonote::txout_to_key>(td.m_tx.vout[td.m_internal_output_index].target).key;
     bool r = cryptonote::generate_key_image_helper(m_account.get_keys(), m_subaddresses, out_key, tx_pub_key, additional_tx_pub_keys, td.m_internal_output_index, in_ephemeral, td.m_key_image, m_account.get_device());
     THROW_WALLET_EXCEPTION_IF(!r, error::wallet_internal_error, "Failed to generate key image");
     expand_subaddresses(td.m_subaddr_index);
     td.m_key_image_known = true;
     td.m_key_image_partial = false;
-    THROW_WALLET_EXCEPTION_IF(in_ephemeral.pub != boost::get<cryptonote::txout_to_key>(td.m_tx.vout[td.m_internal_output_index].target).key,
+    THROW_WALLET_EXCEPTION_IF(in_ephemeral.pub != out_key,
         error::wallet_internal_error, "key_image generated ephemeral public key not matched with output_key at index " + boost::lexical_cast<std::string>(i));
 
     m_key_images[td.m_key_image] = m_transfers.size();
     m_pub_keys[td.get_public_key()] = m_transfers.size();
-    m_transfers.push_back(td);
+    m_transfers.push_back(std::move(td));
   }
 
   return m_transfers.size();