Entry Group Empty State
To achieve an empty state for my group (When there's no entries existing within that group). I re-assembled the array and outputted them in a certain order - allowing for an if to come alive when there actually wasn't any status available.

{% set proposals = craft.entries.section('proposals').authorId(currentUser.id) %}
{% set proposalsByGroup = proposals|group('proposalStatus') %}

{% for status in ['pending','accepted','delivered'] %}

  {% if proposalsByGroup[status] is defined %}
    {% set entriesInStatus = proposalsByGroup[status] %}
          {{ status }}
          {% for proposal in entriesInStatus %}
             Hello.
          {% endfor %}
  {% else %}
          {{ status }}
          Nothing here, but still gives a status that you've set above.
  {% endif %}
{% endfor %}