fixes ignored readable event in WrappingIterator

Author: jacoscaz

asynciterator.ts

@@ -2038,13 +2038,17 @@ export class WrappingIterator<T> extends AsyncIterator<T> {
     this._source._destination = this;
     this._source.on('end', destinationClose);
     this._source.on('error', destinationEmitError);
-    this._source.on('readable', () => this.emit('readable'));
     this._source.on('readable', destinationSetReadable);
     this.readable = true;
   }
 
   read(): T | null {
-    return this._source ? this._source.read() : null;
+    let item = null;
+    if (this._source)
+      item = this._source.read();
+    if (!item)
+      this.readable = false;
+    return item;
   }
 
   protected _end(destroy: boolean = false) {