Describe the bug
When I try to close a modal clicking outside it, the console throws an error and it doesn't calls the action to close in the controller. I think it's a problem with the latest versions of Ember and the compatibility with the library modal-dialog.

This is because this.get('onClose') in model-dialog is a string instead a function.

To Reproduce
Steps to reproduce the behavior:

1. Open a md-modal.
2. Click outside the modal.
3. In the console, you're going to see the following: TypeError: this.get(...) is not a function.

Expected behavior
It should call the controller action.

Desktop (please complete the following information):

• Browser Chrome 73 and Firefox
• Ember 3.4.4

Additional context
I think that's going to need to remove sendAction in the following lines. Like this:

  cancel() {
    this.close();
  },

  actions: {
    closeModal() {
      this.close();
    }
}

Not tested. Could it have some problem with older Ember versions? The change is very little so I'm going to make and discuss about it after being done.