[Bug]: Displaying "unknown" during NFT send

### Describe the bug

We're displaying "Unknown" during NFT sends within the section that shows how many NFTs are available to send.

### Expected behavior

_No response_

### Screenshots/Recordings

### Steps to reproduce

1. Start a NFT send

### Error messages or log output

```shell

```

### Where was this bug found?

Live version (from official store)

### Version

13.11.2

### Build type

None

### Browser

Brave

### Operating system

MacOS

### Hardware wallet

_No response_

### Additional context

_No response_

### Severity

_No response_

Start by reproducing an NFT send in the MetaMask extension, as described in the issue, and inspect the UI section that shows how many NFTs are available to send. Use the attached screenshot and version 13.11.2 as context; done means the section displays the available NFT count instead of "Unknown".

Written by the indexing model from the issue text.