Three.js - this.passes[Symbol.iterator] is not a function

I am using the following postprocessing engine for a three.js project:

https://github.com/vanruesc/postprocessing

It works very well, however when I play audio on the website, I get this error:

this.passes[Symbol.iterator] is not a function

The error points to this iterator:

for (var _iterator16 = this.passes[Symbol.iterator](), _step16; !(_iteratorNormalCompletion16 = (_step16 = _iterator16.next()).done); _iteratorNormalCompletion16 = true) {
  var pass = _step16.value;

  if (pass.enabled) {
    pass.render(renderer, inputBuffer, outputBuffer, deltaTime, stencilTest);

    if (pass.needsSwap) {
      if (stencilTest) {
        copyPass.renderToScreen = pass.renderToScreen;
        context = renderer.getContext();
        stencil = renderer.state.buffers.stencil;
        stencil.setFunc(context.NOTEQUAL, 1, 0xffffffff);
        copyPass.render(renderer, inputBuffer, outputBuffer, deltaTime, stencilTest);
        stencil.setFunc(context.EQUAL, 1, 0xffffffff);
      }

      buffer = inputBuffer;
      inputBuffer = outputBuffer;
      outputBuffer = buffer;
    }

    if (pass instanceof MaskPass) {
      stencilTest = true;
    } else if (pass instanceof ClearMaskPass) {
      stencilTest = false;
    }
  }
}   

Thank you for any help