`ArgumentError` in `_findCloseNode` when tapping an empty EditorState

Start in lib/src/editor/editor_component/service/selection/shared.dart, focusing on getNodeInOffset and its call to _findCloseNode. Reproduce the tap with Document.blank(withInitialText: false), then verify the empty-node case returns null and the editor no longer throws an ArgumentError during selection handling.

Describe the bug

When EditorState is initialized with a completely empty Document (i.e. containing 0 nodes, such as Document.blank(withInitialText: false)) and the user taps inside the editor, an ArgumentError: Invalid argument(s): 0 is thrown by _findCloseNode in shared.dart.

Steps to Reproduce

1. Initialize EditorState with Document.blank(withInitialText: false).
2. Render AppFlowyEditor.
3. Tap on the editor surface.
4. The application throws the following exception:

ArgumentError: Invalid argument(s): 0

Stack trace:
EditorStateSelection._findCloseNode
EditorStateSelection.getNodeInOffset
_MobileSelectionServiceWidgetState.getNodeInOffset
_MobileSelectionServiceWidgetState.getPositionInOffset
_MobileSelectionServiceWidgetState._onTapUpAndroid

Expected Behavior

The editor should handle the empty node list gracefully without throwing an exception, likely by returning null from getNodeInOffset and safely ignoring the tap selection.

Root Cause Analysis

In lib/src/editor/editor_component/service/selection/shared.dart, the getNodeInOffset function attempts to guard against invalid bounds:

    if (start < 0 && end >= sortedNodes.length) {
      return null;
    }

If sortedNodes is empty, getNodeInOffset receives start = 0 and end = -1.
The condition end >= sortedNodes.length evaluates to -1 >= 0, which is false. Because of the && operator, the bounds check fails to catch the empty array case.

The code then proceeds to call _findCloseNode(sortedNodes, 0, -1).
Inside _findCloseNode, the binary search loop is skipped, and it returns:

    return min.clamp(start, end);

Since min = 0, start = 0, and end = -1, 0.clamp(0, -1) throws an ArgumentError: Invalid argument(s): 0 because the lower bound is greater than the upper bound.

Proposed Fix

Change the bounds check in getNodeInOffset to:

    if (start < 0 || end >= sortedNodes.length || start > end) {
      return null;
    }

Or alternatively, add an explicit check for empty lists:

    if (sortedNodes.isEmpty) return null;