fix: Back from AddressToken clears the selected token (closes #751)

AddressDetail's show() clears the token, but "Back" onto a screen already drawn
only unhides it. Send and Receive then kept using the token from AddressToken,
whatever Send's dropdown showed. "Back" now clears the token and puts the
dropdown on ETH.

Model: opus-5-5

src/popup/views/addressToken.js

@@ -360,6 +360,11 @@ function init(_ctx) {
     });
 
     $("btn-address-token-back").addEventListener("click", () => {
+        // AddressDetail's show() clears the token, but Back onto a drawn
+        // screen only unhides it. "Send" below may have left the dropdown on
+        // the token as well.
+        state.selectedToken = null;
+        $("send-token").value = "ETH";
         goBack();
     });