Fix null checking

src/Avalonia.Controls/DefinitionBase.cs

@@ -110,11 +110,11 @@ namespace Avalonia.Controls
         /// </remarks>
         internal void OnUserSizePropertyChanged(AvaloniaPropertyChangedEventArgs e)
         {
-            if (InParentLogicalTree)
+            if (Parent != null)
             {
                 if (_sharedState != null)
                 {
-                    _sharedState.Invalidate();
+                    _sharedState?.Invalidate();
                 }
                 else
                 {
@@ -129,21 +129,7 @@ namespace Avalonia.Controls
                 }
             }
         }
-
+ 
-        /// <remarks>
-        /// This method needs to be internal to be accessable from derived classes.
-        /// </remarks>
-        internal static void OnUserMinSizePropertyChanged(AvaloniaObject d, AvaloniaPropertyChangedEventArgs e)
-        {
-            DefinitionBase definition = (DefinitionBase)d;
-
-            if (definition.InParentLogicalTree)
-            {
-                Grid parentGrid = (Grid)definition.Parent;
-                parentGrid.InvalidateMeasure();
-            }
-        }
-
         /// <remarks>
         /// This method reflects Grid.SharedScopeProperty state by setting / clearing
         /// dynamic property PrivateSharedSizeScopeProperty. Value of PrivateSharedSizeScopeProperty
@@ -317,14 +303,6 @@ namespace Avalonia.Controls
         /// </summary>
         internal abstract double UserMaxSizeValueCache { get; }
 
-        /// <summary>
-        /// Protected. Returns <c>true</c> if this DefinitionBase instance is in parent's logical tree.
-        /// </summary>
-        internal bool InParentLogicalTree
-        {
-            get { return (_parentIndex != -1); }
-        }
-
         internal Grid Parent { get; set; }
 
         /// <summary>
@@ -349,7 +327,7 @@ namespace Avalonia.Controls
         {
             DefinitionBase definition = (DefinitionBase)d;
 
-            if (definition.InParentLogicalTree)
+            if (definition.Parent != null)
             {
                 string sharedSizeGroupId = (string)e.NewValue;
 
@@ -421,7 +399,7 @@ namespace Avalonia.Controls
         {
             DefinitionBase definition = (DefinitionBase)d;
 
-            if (definition.InParentLogicalTree)
+            if (definition.Parent != null)
             {
                 SharedSizeScope privateSharedSizeScope = (SharedSizeScope)e.NewValue;
 
@@ -787,4 +765,4 @@ namespace Avalonia.Controls
             PrivateSharedSizeScopeProperty.Changed.AddClassHandler<DefinitionBase>(OnPrivateSharedSizeScopePropertyChanged);
         }
     }
-}
+}

src/Avalonia.Controls/Grid.cs

@@ -1726,7 +1726,7 @@ namespace Avalonia.Controls
         /// </summary>
         /// <param name="definitions">Array of definitions to process.</param>
         /// <param name="finalSize">Final size to lay out to.</param>
-        /// <param name="rows">True if sizing row definitions, false for columns</param>
+        /// <param name="columns">True if sizing row definitions, false for columns</param>
         private void SetFinalSize(
             IReadOnlyList<DefinitionBase> definitions,
             double finalSize,
@@ -2303,29 +2303,7 @@ namespace Avalonia.Controls
                 }
             }
         }
-
+ 
-        /// <summary>
-        /// Returns <c>true</c> if ColumnDefinitions collection is not empty
-        /// </summary>
-        public bool ShouldSerializeColumnDefinitions()
-        {
-            ExtendedData extData = ExtData;
-            return (extData != null
-                    && extData.ColumnDefinitions != null
-                    && extData.ColumnDefinitions.Count > 0);
-        }
-
-        /// <summary>
-        /// Returns <c>true</c> if RowDefinitions collection is not empty
-        /// </summary>
-        public bool ShouldSerializeRowDefinitions()
-        {
-            ExtendedData extData = ExtData;
-            return (extData != null
-                    && extData.RowDefinitions != null
-                    && extData.RowDefinitions.Count > 0);
-        }
-
         /// <summary>
         /// Synchronized ShowGridLines property with the state of the grid's visual collection
         /// by adding / removing GridLinesRenderer visual.
@@ -3392,4 +3370,4 @@ namespace Avalonia.Controls
             private static readonly Pen _evenDashPen;  //  second pen to draw dash
         }
     }
-}
+}