fix: the ETH line reads unknown at an address no refresh has read (closes #736)

An address's ETH balance is now null until a refresh has read it. That covers
a new address, a new wallet, addresses a wallet scan finds, and every address
after a network switch.

Its line reads `quantity unknown`, Home's balance `unknown (ETH)`, and Send
`Current balance: unknown (ETH)`. Max says the balance is unknown. Send is no
longer refused as zero. The address has no total, and DeleteAddress keeps its
warning.

A refresh also deletes `balanceNotFetched` only when it read every address in
the stored record.

Model: opus-5-5

tests/addressValue.test.js

@@ -125,6 +125,14 @@ describe("the value of an address, and whether it is the whole value", () => {
         expect(getAddressValue(addr)).toEqual({ usd: 0, partial: false });
     });
 
+    // No total can include an ETH balance no refresh has read, and "unpriced
+    // tokens only" would be untrue of an address with nothing known at all.
+    test("an ETH balance no refresh has read means no value", () => {
+        const addr = { address: "0x1", balance: null, tokenBalances: [] };
+        expect(getAddressValue(addr)).toEqual({ usd: null, partial: false });
+        expect(formatAddressTotal(getAddressValue(addr))).toBe("");
+    });
+
     // Before the first price fetch, and on testnet, nothing is knowable: that
     // is a third state, and it stays distinct from both of the others.
     test("no prices at all means no value, not an incomplete one", () => {