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/addressToken.js

@@ -172,8 +172,8 @@ function renderBalance() {
             (t) => t.address.toLowerCase() === id,
         );
         // null when the scale is unknown, or when no refresh has read the
-        // balance of a token just added: no quantity to show, and none to
-        // price. balanceLine() states that rather than printing 0.0000.
+        // token's balance: no quantity to show, and none to price.
+        // balanceLine() states that rather than printing 0.0000.
         if (tb) amount = unknownableAmount(tb.balance);
         else amount = tracked && tracked.balanceNotFetched ? null : 0;
         price = getPrice(tokenId);