Wondering why this code throws no error at: changeValue("e");

Test.as

package
{

    import flash.display.Sprite;

    public class Test extends Sprite
    {
        public function Test()
        {
            var a:Value = new Value();
                a.str = "a";
     
            const changeValue: Function = function( to: String ): void
            {
                trace( this );
                this.str = to;
            }

            changeValue.apply(a,["c"]);
            trace( a.str ); // "c"
            changeValue.call(a, "d");
            trace( a.str ); // "d"
            changeValue("e"); // this is [global], has no .str method but no error is thrown
            trace( a.str ); // "d" 

        }
    }
}

internal class Value
{
    public var str:String;
}