Fix memory leak.

lib/iteratorCaller.js

@@ -21,8 +21,10 @@ class IteratorCallerStream extends SwiftTransformStream {
 
         // Execute the iterator
         // Note that the iterator can throw synchronously as well as return non-promise values
-        return Promise.resolve()
-        .then(() => this._iterator(data))
+        new Promise((resolve, reject) => {
+            Promise.resolve(this._iterator(data))
+            .then(resolve, reject);
+        })
         .then(() => callback(null, data), (err) => callback(err))
         // Equivalent to .done()
         .catch((err) => {

lib/iteratorCallerBulk.js

@@ -54,8 +54,10 @@ class IteratorCallerBulkStream extends TransformStream {
 
         // Execute the iterator
         // Note that the iterator can throw synchronously as well as return non-promise values
-        return Promise.resolve()
-        .then(() => this._iterator(this._buffer))
+        return new Promise((resolve, reject) => {
+            Promise.resolve(this._iterator(this._buffer))
+            .then(resolve, reject);
+        })
         .then(() => { this._buffer = []; });
     }
 }