feat: no-data view support added.

[sushil7271]

Title: Implement "No Data" Handling and View in PagedDataTable Widget

Description

Problem:

Previously, the table widget did not have a clear way to handle situations where no data was available to display. This could lead to an empty or confusing UI for the user.

Solution:

This pull request introduces robust support for "no data" scenarios in the PagedDataTable widget by:

1. New noDataView Widget Parameter:
   • Added a new optional widget parameter called noDataView to the PagedDataTable widget.
   • This parameter allows developers to provide a custom widget to display when the table has no data.
   • If this parameter is not set, the code will use a SizedBox.shrink().
2. Conditional "No Data" View Display:
   • Implemented a conditional check within the table widget to detect "no data" situations.
   • The condition is as follows: if (tableController._state == _TableState.noData && tableController._currentDataset.isEmpty).
   • When this condition is met, the table will display the noDataView widget (if provided) instead of the empty table.
3. New _TableState.noData State:
   • Added a new state, _TableState.noData, to the _TableState enum.
   • This state specifically represents the "no data" condition of the table.
4. Triggering Notification Listeners:
   • Ensured that the notification listeners are correctly triggered when the table enters the _TableState.noData state. This ensures that the UI updates appropriately.
   • The notifyListeners method was called in the correct place.

Impact:

• Improved User Experience: Users will now see a clear and informative message or custom view when no data is available in the table.
• Flexibility: Developers can customize the "no data" view to match the design and requirements of their application.
• Robustness: The table widget is now more robust in handling empty data scenarios.
• Readability: the code is now more readable.

Files Changed:

• controller.dart: Modified to add the new state, the conditional check, and trigger the notification.
• paged_datatable.dart: (If present) Added the noDataView parameter to the Table widget and conditional check.

How to Test:

1. Simulate No Data: Modify your data fetching logic or filters to simulate a scenario where the pagedDataTable receives no data.
2. Verify No Data View: Check that the noDataView widget (if provided) is displayed in the table area.
3. Verify Empty Space: If you don't use noDataView, ensure that an empty space is displayed.
4. Verify state: Check that the state changes correctly.
5. Verify notification: Check that the listeners are called.

CC: @tomasweigenast