[Foundation] NSArray<T>.FromNSObjects will never return null objects. Fixes #19622. (#19627)

NSArray<T>.FromNSObjects will never return a null object, because
NSArray.FromObjects won't (according to Apple's headers).

Fixes #19622.

Author: rolfbjarne

src/Foundation/NSArray_1.cs

@@ -48,15 +48,15 @@ internal NSArray (NativeHandle handle) : base (handle)
 		{
 		}
 
-		static public NSArray<TKey>? FromNSObjects (params TKey [] items)
+		static public NSArray<TKey> FromNSObjects (params TKey [] items)
 		{
 			if (items is null)
 				throw new ArgumentNullException (nameof (items));
 
 			return FromNSObjects (items.Length, items);
 		}
 
-		static public NSArray<TKey>? FromNSObjects (int count, params TKey [] items)
+		static public NSArray<TKey> FromNSObjects (int count, params TKey [] items)
 		{
 			if (items is null)
 				throw new ArgumentNullException (nameof (items));
@@ -71,7 +71,7 @@ internal NSArray (NativeHandle handle) : base (handle)
 				Marshal.WriteIntPtr (buf, (int) (i * IntPtr.Size), h);
 			}
 			IntPtr ret = NSArray.FromObjects (buf, count);
-			var arr = Runtime.GetNSObject<NSArray<TKey>> (ret);
+			var arr = Runtime.GetNSObject<NSArray<TKey>> (ret)!;
 			Marshal.FreeHGlobal (buf);
 			return arr;
 		}