allow null collection for table type parameters

src/Pingmint.CodeGen.Sql/CodeFile.cs

@@ -173,19 +173,17 @@ public String GenerateCode()
 
                 using var tableClass = code.PartialClass("public sealed", dataTableClassName, "DataTable");
                 code.Line("public {0}() : this(new List<{1}>()) {{ }}", dataTableClassName, rowClassName);
-                code.Line("public {0}(List<{1}> rows) : base()", dataTableClassName, rowClassName);
+                code.Line("public {0}(List<{1}>? rows) : base()", dataTableClassName, rowClassName);
                 using (code.CreateBraceScope())
                 {
-                    code.Line("ArgumentNullException.ThrowIfNull(rows);");
-                    code.Line();
                     foreach (var col in record.Properties)
                     {
                         var allowDbNull = col.ColumnIsNullable ? "true" : "false";
                         var maxLength = (col.MaxLength is short s && col.FieldType?.ToLowerInvariant() == "string") ? $", MaxLength = {s}" : String.Empty; // the default is already "-1", so we do not have to emit this in code.
                         var propertyTypeName = col.FieldTypeWithoutNullable;
                         code.Line("base.Columns.Add(new DataColumn() {{ ColumnName = \"{0}\", DataType = typeof({1}), AllowDBNull = {2}{3} }});", col.ColumnName, propertyTypeName, allowDbNull, maxLength);
                     }
-                    using (code.ForEach("var row in rows"))
+                    using (code.ForEach("var row in rows ?? []"))
                     {
                         var parameterBuilder = String.Empty;
                         foreach (var col in record.Properties)

src/Pingmint.CodeGen.Sql/Pingmint.CodeGen.Sql.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <Version>0.47</Version>
+    <Version>0.48</Version>
     <OutputType>Exe</OutputType>
     <TargetFramework>net10.0</TargetFramework>
     <LangVersion>latest</LangVersion>