fix: say a contract creation has no recipient instead of a blank line (closes #250)

A transaction with no `to` showed a blank address, with a colour dot whose
colour was `undefined`, on the wait, success and error screens, the
transaction detail view and the history rows on Home, AddressDetail and
AddressToken. The approval screen showed "(contract creation)".

All of them now say "This transaction creates a new contract. It has no
recipient." The three history lists draw a row's counterparty lines through
one helper in helpers.js. A transaction with a real `to` is unchanged. The
new test drives each screen and list both ways.

Model: opus-5-5

src/popup/views/transactionDetail.js

@@ -7,6 +7,7 @@ const {
     showFlash,
     flashCopyFeedback,
     addressTitle,
+    CONTRACT_CREATION_TEXT,
     addressDotHtml,
     escapeHtml,
     isoDate,
@@ -94,13 +95,18 @@ function render() {
     $("tx-detail-hash").innerHTML = txHashHtml(tx.hash);
 
     const fromTitle = addressTitle(tx.from, state.wallets);
-    const toTitle = addressTitle(tx.to, state.wallets);
     $("tx-detail-from").innerHTML = txAddressHtml(
         tx.from,
         tx.fromEns,
         fromTitle,
     );
-    $("tx-detail-to").innerHTML = txAddressHtml(tx.to, tx.toEns, toTitle);
+    // A contract creation has no recipient: transactions.js gives it `to: ""`.
+    if (tx.to) {
+        const toTitle = addressTitle(tx.to, state.wallets);
+        $("tx-detail-to").innerHTML = txAddressHtml(tx.to, tx.toEns, toTitle);
+    } else {
+        $("tx-detail-to").innerHTML = escapeHtml(CONTRACT_CREATION_TEXT);
+    }
 
     // Exact amount (full precision, copyable)
     const detailSym = displaySymbol(tx.symbol);