fix: validate null arguments in X10D.Unity

The CA runs are really testing me today.

X10D.Unity/src/ComponentExtensions.cs

@@ -14,8 +14,14 @@ public static class ComponentExtensions
     /// <param name="component">The component whose child components to retrieve.</param>
     /// <typeparam name="T">The type of the components to retrieve.</typeparam>
     /// <returns>An array <typeparamref name="T" /> representing the child components.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="component" /> is <see langword="null" />.</exception>
     public static T[] GetComponentsInChildrenOnly<T>(this Component component)
     {
+        if (component == null)
+        {
+            throw new ArgumentNullException(nameof(component));
+        }
+
         return component.gameObject.GetComponentsInChildrenOnly<T>();
     }
 }

X10D.Unity/src/Drawing/PolyhedronExtensions.cs

@@ -14,8 +14,14 @@ public static class PolyhedronExtensions
     /// </summary>
     /// <param name="polyhedron">The polyhedron whose vertices to update.</param>
     /// <param name="vertex">The vertex to add.</param>
+    /// <exception cref="ArgumentNullException"><paramref name="polyhedron" /> is <see langword="null" />.</exception>
     public static void AddVertex(this Polyhedron polyhedron, Vector3Int vertex)
     {
+        if (polyhedron is null)
+        {
+            throw new ArgumentNullException(nameof(polyhedron));
+        }
+
         polyhedron.AddVertex(vertex.ToSystemVector());
     }
 
@@ -24,8 +30,14 @@ public static class PolyhedronExtensions
     /// </summary>
     /// <param name="polyhedron">The polyhedron whose vertices to update.</param>
     /// <param name="vertex">The vertex to add.</param>
+    /// <exception cref="ArgumentNullException"><paramref name="polyhedron" /> is <see langword="null" />.</exception>
     public static void AddVertex(this Polyhedron polyhedron, Vector3 vertex)
     {
+        if (polyhedron is null)
+        {
+            throw new ArgumentNullException(nameof(polyhedron));
+        }
+
         polyhedron.AddVertex(vertex.ToSystemVector());
     }
 
@@ -34,8 +46,23 @@ public static class PolyhedronExtensions
     /// </summary>
     /// <param name="polyhedron">The polyhedron whose vertices to update.</param>
     /// <param name="vertices">The vertices to add.</param>
+    /// <exception cref="ArgumentNullException">
+    ///     <para><paramref name="polyhedron" /> is <see langword="null" />.</para>
+    ///     -or-
+    ///     <para><paramref name="vertices" /> is <see langword="null" />.</para>
+    /// </exception>
     public static void AddVertices(this Polyhedron polyhedron, IEnumerable<Vector3Int> vertices)
     {
+        if (polyhedron is null)
+        {
+            throw new ArgumentNullException(nameof(polyhedron));
+        }
+
+        if (vertices is null)
+        {
+            throw new ArgumentNullException(nameof(vertices));
+        }
+
         foreach (Vector3Int vertex in vertices)
         {
             polyhedron.AddVertex(vertex);
@@ -47,8 +74,23 @@ public static class PolyhedronExtensions
     /// </summary>
     /// <param name="polyhedron">The polyhedron whose vertices to update.</param>
     /// <param name="vertices">The vertices to add.</param>
+    /// <exception cref="ArgumentNullException">
+    ///     <para><paramref name="polyhedron" /> is <see langword="null" />.</para>
+    ///     -or-
+    ///     <para><paramref name="vertices" /> is <see langword="null" />.</para>
+    /// </exception>
     public static void AddVertices(this Polyhedron polyhedron, IEnumerable<Vector3> vertices)
     {
+        if (polyhedron is null)
+        {
+            throw new ArgumentNullException(nameof(polyhedron));
+        }
+
+        if (vertices is null)
+        {
+            throw new ArgumentNullException(nameof(vertices));
+        }
+
         foreach (Vector3 vertex in vertices)
         {
             polyhedron.AddVertex(vertex);

X10D.Unity/src/GameObjectExtensions.cs

@@ -13,8 +13,14 @@ public static class GameObjectExtensions
     /// <param name="gameObject">The game object whose child components to retrieve.</param>
     /// <typeparam name="T">The type of the components to retrieve.</typeparam>
     /// <returns>An array <typeparamref name="T" /> representing the child components.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="gameObject" /> is <see langword="null" />.</exception>
     public static T[] GetComponentsInChildrenOnly<T>(this GameObject gameObject)
     {
+        if (gameObject == null)
+        {
+            throw new ArgumentNullException(nameof(gameObject));
+        }
+
         Transform rootTransform = gameObject.transform;
         var components = new List<T>(gameObject.GetComponentsInChildren<T>());