[Keybase Desktop] Keybase Client Breaks When Client Selects Empty File

# Description

The desktop client breaks when a user selects a file with a size of zero bytes.

# Reproduction Steps

1. Open Keybase Client.
2. `touch NULL`
3. Open crypto tools.
4. Select the empty file.

# Result

The checkbox option UI disappears in the selected tab; the other tabs are unaffected.

Attempting to continue the process will result in further broken UI; however, the process will complete successfully.

# Troubleshooting

The issue is not resolved by closing the application; in order to resolve the issue, every Keybase process must be terminated manually.

Reproduce the failure in the Keybase desktop client's crypto tools using the listed empty-file steps. No source file or test is identified, so first locate the selected-file and checkbox UI entry points; done means selecting a zero-byte file leaves the tab usable and the process can continue without breaking the client.

Written by the indexing model from the issue text.