Prevented setting 0 to ColumnSpan or RowSpan.

[abenedik]

The current code allows setting 0 to ColumnSpan or RowSpan.

But if this is done, for example, by calling Grid.SetColumSpan(control, 0), the following exception is thrown from Avalonia's layout pass:

ArgumentOutOfRangeException: 'Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index')'

in

>	Avalonia.Base.dll!Avalonia.Collections.AvaloniaList<System.__Canon>.this[int].get(int index) Line 114	C#
 	Avalonia.Controls.dll!Avalonia.Controls.Grid.GetLengthTypeForRange(System.Collections.Generic.IReadOnlyList<Avalonia.Controls.DefinitionBase> definitions = {Avalonia.Controls.ColumnDefinitions}, int start = 0, int count = 0)	Unknown
 	Avalonia.Controls.dll!Avalonia.Controls.Grid.ValidateCellsCore()	Unknown
 	Avalonia.Controls.dll!Avalonia.Controls.Grid.ValidateCells()	Unknown
 	Avalonia.Controls.dll!Avalonia.Controls.Grid.MeasureOverride(Avalonia.Size constraint = {Avalonia.Size})	Unknown
 	Avalonia.Base.dll!Avalonia.Layout.Layoutable.MeasureCore(Avalonia.Size availableSize = {Avalonia.Size}) Line 395	C#
 	Avalonia.Base.dll!Avalonia.Layout.Layoutable.Measure(Avalonia.Size availableSize = {Avalonia.Size}) Line 278	C#
 	Avalonia.Base.dll!Avalonia.Layout.LayoutManager.Measure(Avalonia.Layout.Layoutable control = "Grid (Name = BottomOptionsGrid)") Line 264	C#
 	Avalonia.Base.dll!Avalonia.Layout.LayoutManager.ExecuteMeasurePass() Line 223	C#
 	Avalonia.Base.dll!Avalonia.Layout.LayoutManager.InnerLayoutPass() Line 207	C#
 	Avalonia.Base.dll!Avalonia.Layout.LayoutManager.ExecuteLayoutPass() Line 130	C#

In WPF, the ColumnSpan property immediately throws an ArgumentOfOutRange exception when 0 is set to ColumSpan.

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0055727-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[cla-avalonia]

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[abenedik]

@cla-avalonia agree

[MrJul]

LGTM, thank you!

Grid was ported from WPF, where RowSpan and ColumnSpan correctly have > 0 validation, which was probably lost at some point.