PoseGraph read JSON failed: empty edges. with D405

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### My Question

Hello.

Reconstruction_system is tested with D405, 435, 435i and L515.
For model with IMU sensor, the code works well.

But D405 not works with the error message as following.

[Open3D WARNING] PoseGraph read JSON failed: empty edges.
[Open3D DEBUG] Validating PoseGraph - finished.
[Open3D DEBUG] [GlobalOptimizationLM] Optimizing PoseGraph having 1 nodes and 0 edges.
[Open3D DEBUG] Line process weight : 0.000000
[Open3D DEBUG] [Initial ] residual : 0.000000e+00, lambda : 0.000000e+00
[Open3D DEBUG] Maximum coefficient of right term < 1.000000e-06
[Open3D DEBUG] [GlobalOptimizationLM] Optimizing PoseGraph having 1 nodes and 0 edges.
[Open3D DEBUG] Line process weight : 0.000000
[Open3D DEBUG] [Initial ] residual : 0.000000e+00, lambda : 0.000000e+00
[Open3D DEBUG] Maximum coefficient of right term < 1.000000e-06
[Open3D DEBUG] CompensateReferencePoseGraphNode : reference : 0

My question is...
Does only camera with IMU sensor work to reconstruction system?
or
How can I test the code with D405 or any other model without IMU?

Thank you.