Don't add Panel Logical children twice!

Perspex.Controls/Panel.cs

@@ -57,7 +57,6 @@ namespace Perspex.Controls
                 this.ClearVisualChildren();
                 this.children.Clear();
                 this.children.AddRange(value);
-                this.LogicalChildren.AddRange(value);
             }
         }
 

Tests/Perspex.Controls.UnitTests/PanelTests.cs

@@ -84,6 +84,18 @@ namespace Perspex.Controls.UnitTests
             Assert.Null(child2.GetLogicalParent());
         }
 
+        [Fact]
+        public void Setting_Children_Should_Make_Controls_Appear_In_Panel_Children()
+        {
+            var panel = new Panel();
+            var child = new Control();
+
+            panel.Children = new Controls { child };
+
+            Assert.Equal(new[] { child }, panel.Children);
+            Assert.Equal(new[] { child }, panel.GetLogicalChildren());
+        }
+
         [Fact]
         public void Child_Control_Should_Appear_In_Panel_Children()
         {