dApp crashes when trying to convert specific ERC-20 tokens to sUSD on "Convert" page

[drptbl]

Description: dApp crashes when trying to convert specific ERC-20 tokens to sUSD on "Convert" page.

Prerequisites:

• specific ERC-20 token on the wallet (UNI or RAZOR for example)

Reproduction steps:

1. Go to Kwenta "Convert" page (https://dev.kwenta.io/dashboard/convert)
2. Connect your wallet
3. Select any token (mentioned above, for example "UNI") inside "From" drop-down
4. Type any value inside "From" input field
5. Click on "Approve" button

Current behavior:

• dApp crashes after hitting "Approve" button for "UNI" token

Expected behavior:

• user should be able to convert all assets with success

Screenshots:

Desktop (please complete the following information):

• OS: macOS Big Sur 11.2.2
• Browser: Chrome 89.0.4389.95

[drptbl]

duplicate of #331