fix: a tracked token reads quantity unknown at an address no refresh has read (closes #720)

A new address, a new wallet and a network switch each leave tracked tokens
with no balance entry, so their lines read 0.0000 before any refresh had read
them.

Each of these now sets `balanceNotFetched` on the tracked tokens, and a refresh
already clears it. Their lines read `quantity unknown` until then. Addresses
that the wallet scan finds get the same. A refresh that did not read every
address the page now holds leaves the field set.

Model: opus-5-5

src/popup/views/helpers.js

@@ -430,6 +430,13 @@ function trackToken(token) {
     state.trackedTokens.push({ ...token, balanceNotFetched: true });
 }
 
+// Gives every tracked token `balanceNotFetched: true`, as trackToken() gives a
+// new one. Called when an address is added, before the save: no refresh has
+// read any token's balance at that address.
+function markTrackedTokensNotFetched() {
+    for (const token of state.trackedTokens) token.balanceNotFetched = true;
+}
+
 function balanceLinesForAddress(addr, trackedTokens, showZero) {
     let html = balanceLine(
         nativeCurrency(),
@@ -850,6 +857,7 @@ module.exports = {
     balanceLine,
     balanceLinesForAddress,
     trackToken,
+    markTrackedTokensNotFetched,
     addressHoldsFunds,
     keyMaterialName,
     unknownableAmount,