[BUG] Custom task overview widget only displays tasks from alert-merged cases

[k1ngn7]

Describe the bug
When creating a dashboard widget that displays the number of tasks using the Case Tasks table, the widget only counts tasks associated with cases originating from merged alerts. Tasks created within manually created cases are not included in the widget, even though they exist and are correctly displayed within their respective cases.

To Reproduce
Steps to reproduce the behavior:

1. Populate the DFIR-IRIS instance with both manually created cases and alerts.
2. Merge some alerts into cases.
3. Create one or more tasks in:
   • manually created cases;
   • cases originating from merged alerts.
4. Navigate to Dashboards.
5. Click New Dashboard.
6. Add a new widget with the following configuration:
   • Visualization: Number
   • Field:
     • Table: Case Tasks
     • Column: Task ID
7. Click on Save to save the dashboard.

Expected behavior
The widget should display the total number of tasks across all cases, regardless of whether the case was created manually or originated from a merged alert.

Actual Behavior
The widget only counts tasks belonging to cases that originated from merged alerts. Tasks associated with manually created cases are ignored and are not included in the displayed count.

Desktop (please complete the following information):

• OS: Windows 11
• Browser : Microsoft Edge
• Version : v2.4.28