Full line comment wrongfully converted to same line comment

[DavHau]

Describe the bug
executing nixpkgs-fmt on this:

{
  pkgs ? import <nixpkgs> {},
  lib ? pkgs.lib,
  externalSources ?
    # if called via CLI, load externals via env
    if builtins ? getEnv && builtins.getEnv "d2nExternalSources" != "" then
      builtins.getEnv "d2nExternalSources"
    # load from default dircetory
    else
      ./external,
}:

...results in this

{ pkgs ? import <nixpkgs> { }
, lib ? pkgs.lib
, externalSources ? # if called via CLI, load externals via env
  if builtins ? getEnv && builtins.getEnv "d2nExternalSources" != "" then
    builtins.getEnv "d2nExternalSources"
  # load from default dircetory
  else
    ./external
,
}:

The full line comment originally from line 5 has been converted to a same line comment, so it looks like the comment is about externalSources, which is actually not the case. The comment was about the if statement in the next line

Expected behavior
The original comment of line 5, should remain a full line comment

System information

• nixpkgs-fmt 1.2.0