Issue with multiple screens (macOS ipad sidecar display)

**Describe the bug**
Visualization does not work when a secondary display is connected. I'm using an iPad as a secondary screen in macOS.

**To Reproduce**
Steps to reproduce the behavior:

1. Connect secondary display
2. Draw a point cloud: `open3d.visualization.draw_geometries([pcd])`
3. Get this error:
```
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
in
15 pcd.colors = pcd_colors
16
---> 17 open3d.visualization.draw_geometries([pcd])

RuntimeError: [Open3D ERROR] GLFW Error: Cocoa: Failed to find service port for display
```

**Expected behavior**
I expected the visualization window to open.

**Environment (please complete the following information):**

- Operating system: macOS Big Sur 11.0.1
- Python version: 3.8.5
- Open3D version: 0.10.0
- Is this remote workstation?: no
- How did you install Open3D?: pip

**Additional context**
Once I disconnect the secondary screen, everything goes back to normal and works.