Kanban Board: Adding Task through the Story Card throws an error

Issue Summary

When opening an Story card that is present on the Kanban Board, the Task tabs shows 0 (even if there are tasks associated with this Story), and after hiting edit/Add and filling the needed fields, an error effort hours cannot be empty is thrown.

Steps to Reproduce

1. Go to Kanban Boards-> Click on view board
2. Open one Story Card with a double click
3. Go to the task tab
4. Click on add/Edit
5. Fill all the details and click Add

Expected Results

The Task would be created.

Actual Results

Error effort hours cannot be empty is thrown.

Workaround

To add a Task to the board:

1. Click on the column 3 blue lines
2. Fast add-> Tasks
3. Fill all the details -> Save and Add to board