Token input: Max button not working in multi-token mode

[InakyMaister]

Description

The Max button in the Token Input component does not work when using multi-token mode. Clicking it has no effect on the input value.

Steps to reproduce

1. Go to Token Input demo
2. Select "Multi token"
3. Choose a token with balance
4. Click on "Max" button

Expected vs actual behavior

Expected: Clicking Max fills the input with the user's full token balance.
Actual: Nothing happens -- the input value remains unchanged.

Additional context

[gabitoesmiapodo]

Fixed on #462