[Bug]: Changing Currency to Fiat and back to Token resets the value introduced for Sending USDT

**Describe the bug**
Changing Currency to Fiat and back to Token resets the value introduced for Sending USDT. It seems that this only happens with USDT token and not with others (like DAI, etc).

**Screenshots**

https://user-images.githubusercontent.com/54408225/214088832-e1dc3cf3-5232-4b74-8384-ec8650bd5091.mp4

**To Reproduce**
_Steps to reproduce the behavior_
1. Select Mainnet
2. Import USDT token `0xdac17f958d2ee523a2206206994597c13d831ec7`
3. Click on USDT token
4. Click Send
5. Add any Recipient
6. Add amount
7. Click to convert to Fiat
8. Click to convert to USDT -- see amount introduced in step 6 is now reset to 0

**Expected behavior**
Amount value should not be reset after converting to Fiat and back to USDT.

**Smartphone (please complete the following information):**

- Device: Samsung SM-A217F
- OS: Android 11.0
- App Version: v5.12.3 (1033)

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_to be added after bug submission by internal support / PM_
**Severity**

- How critical is the impact of this bug on a user?
- Add stats if available on % of customers impacted
- Is this visible to all users?
- Is this tech debt?

Reproduce the issue in the mobile app using the listed USDT send flow, then trace the amount handling when switching from USDT to fiat and back. Done means the entered amount remains unchanged after the conversion, including for the supplied USDT contract; no source file or test is named in the issue.

Written by the indexing model from the issue text.