Gains are not recorded if interest has no unit

[SparkyPotato]

Describe your Environment
OS: Windows 11
Paisa Version: 0.7.1
App Variant: Desktop

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Using the sample journal below, the total gains on the dashboard will be 0, as will the gains under Assets > Gain. If a currency is added to the second transaction, the gains are handled correctly.

Expected behavior
The gains should be treated as the default currency even without a unit.

Journal

2024/01/10 Opening
    Assets:Savings:Bank    1000
    Equity:Opening

2024/10/29
    Assets:Savings:Bank    10
    Income:Interest:Bank