Error applying expression with STACReader : "NumExpr 2 does not support Unicode as a dtype."

[emmanuelmathot]

Problem description

On titiler, doing a request similar to /stac/tiles/WebMercatorQuad/9/451/76.png?url=s3%3A%2F%2Fdc-development-catalog%2Fcalls%2Fcall-969%2FcalibratedDatasets%2FS2A_MSIL2A_20230928T042551_N0509_R133_T54XVM_20230928T053752-calibrated%2FS2A_MSIL2A_20230928T042551_N0509_R133_T54XVM_20230928T053752-calibrated.json&rescale=0%2C1&resampling_method=average&resampling=nearest&expression=where((s2cloudless_clp%3E0.5)%2C1%2C0)%3B&asset_as_band=true

Titiler returns the following error:

{
  "detail": "NumExpr 2 does not support Unicode as a dtype."
}

The error is raised when the expression parameter is set.

Expected Output

Correctly processed tile

Environment Information

Titiler from 0.14.0 to 0.18.0
container ghcr.io/developmentseed/titiler:0.18.0 + boto3 and rio-stac

Analysis

I could reproduce the error in rio-tiler in the following branch: https://github.com/emmanuelmathot/rio-tiler/tree/U17