fix: SectionPanel tuntime ChildrenSoruce change

GSS2.UI.Core/SectionPanel.cs

@@ -25,6 +25,8 @@ public class SectionPanel : Panel
                 return value;
             if (sectionPanel.Cyclic)
                 return value;
+            if (sectionPanel.Children.Count() == 0)
+                return 0;
             return Math.Clamp(value, 0, sectionPanel.Children.Count() - 1);
         });
     public int CurrentIndex
@@ -119,6 +121,14 @@ public class SectionPanel : Panel
 
                 foreach (var control in controls)
                     panel.Children.Add(control);
+
+                if (_initialized)
+                {
+                    _childIndeces.Clear();
+                    foreach (var (i, child) in Children.Enumerate())
+                        _childIndeces.Add(child, i);
+                    _initialized = true;
+                }
             }
             panel.InvalidateArrange();
         });