Rewatch (12.3.0) panics with a multichar em-dash on a line that bsc warnings wraps

1

Minimal reproduction:

let f = (~a, ~b, ~c) => ()

@doc("generic placeholder text with no real source disclosed here ....—trailing text so the line is long enough to wrap onto a second row")
let _g = 1

Panics with:

thread 'main' (39728) panicked at src/build/compile.rs:791:18:
stdout should be non-null: Utf8Error { valid_up_to: 441, error_len: Some(2) }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

rescript.json is:

{
  "name": "rewatch-panic-reproduction",
  "sources": { "dir": "src", "subdirs": true },
  "package-specs": { "module": "esmodule" },
  "warnings": { "number": "+27" }
}

package.json is:

{
  "name": "rewatch-panic-reproduction",
  "version": "0.0.0",
  "private": true,
  "dependencies": {
    "rescript": "12.3.0"
  }
}