Use `allowEmpty` parameter in Split

(cherry picked from commit b7a66a820b88002e734a8e7e7c31992cb7d37fdd)

modules/mono/glue/GodotSharp/GodotSharp/Core/StringExtensions.cs

@@ -1109,7 +1109,7 @@ namespace Godot
         // </summary>
         public static string[] Split(this string instance, string divisor, bool allowEmpty = true)
         {
-            return instance.Split(new[] { divisor }, StringSplitOptions.RemoveEmptyEntries);
+            return instance.Split(new[] { divisor }, allowEmpty ? StringSplitOptions.None : StringSplitOptions.RemoveEmptyEntries);
         }
 
         // <summary>