Fix 'Reset' button resetting 'Last Solved On' dates before modal confirmation.

[AvilaAndre]

Description

When the 'Reset' button is pressed a modal is shown and the list checkedAt gets cleared before the confirmation.
It is expected that the list is only deleted once the reset is confirmed.

How to reproduce:

1. Mark some questions as completed - the date will be shown on the right and will appear on local storage.
2. Press the 'Reset' button and do nothing else.
3. Reload the page to be visualize the missing dates on the 'Last Solved On' column.

Screenshots

After marking two questions as completed.

After opening the 'Reset' modal.

After reloading the page.

[seanprashad]

Fixed with #382