test: cover every control that refuses a defective wallet (closes #254)

Each control that leads to a signature or to the private key now has a
test that it refuses a defective wallet before decrypting anything: Send
on the main, address and token screens, Export Private Key, and both
approval screens, as drawn and as clicked.

Send on the confirmation screen had no such check. The Send buttons
stand in front of it, but the popup reopens onto it from a saved view,
so it now refuses the same way.

The comments that said the wallet's key cannot be derived now say that
getSignerForAddress refuses it, and the walletDefects module comment
names both earlier import paths.

Model: opus-5-5

src/popup/views/confirmTx.js

@@ -21,6 +21,7 @@ const {
 } = require("./helpers");
 const { state, currentNetwork } = require("../../shared/state");
 const { getSignerForAddress } = require("../../shared/wallet");
+const { walletDefect } = require("../../shared/walletDefects");
 const { decryptWithPassword } = require("../../shared/vault");
 const { formatUsd, getPrice } = require("../../shared/prices");
 const { getProvider } = require("../../shared/balances");
@@ -537,6 +538,15 @@ function init(_ctx) {
     onViewLeave("confirm-tx", clearPassword);
 
     $("btn-confirm-send").addEventListener("click", async () => {
+        const wallet = state.wallets[state.selectedWallet];
+        // Every Send button refuses a defective wallet before this screen,
+        // but the popup also reopens onto it from a saved view.
+        const defect = walletDefect(wallet);
+        if (defect) {
+            showError("confirm-tx-password-error", defect.shortMessage);
+            return;
+        }
+
         const password = $("confirm-tx-password").value;
         if (!password) {
             showError(
@@ -546,7 +556,6 @@ function init(_ctx) {
             return;
         }
 
-        const wallet = state.wallets[state.selectedWallet];
         let decryptedSecret;
         hideError("confirm-tx-password-error");