How do I hide tags in a category that have no entries?

Question

Entries can have one of two categories and one tag. (People = entries | program = categories | year = tag)

On the pages I'd like to display entries related to the category and grouped by tag. However, I don't want the tag to display if there are no entries with that tag and in that category.

The following code works, but it displays empty tags that I'd like hidden.

{% set entryIds = craft.entries.section('fellows').ids() %}
{% set tags = craft.tags.relatedTo({ sourceElement: entryIds }).groupId(2).find() | reverse %}
   {% for tag in tags %}
      <h3>{{ tag.slug }} {{ category.title }}</h3>
          {% for entry in craft.entries({
                            relatedTo: [
                              'and',
                              { targetElement: category },
                              { targetElement: tag },
                              ],
                              limit: (null),
                              }) %}
           {% include '_entryblock.twig' %} 
           {% endfor %} 
    {% endfor %} 

This currently displays the following — but I don't want it to display 2018 in Program A or 2017 in Program B since neither of those have entries.

Program A:

/program-a (category)
  |__2018 (tag)
  |__2017
       |__Bono (entry)
       |__The Edge
  |__2016
       |__Ringo
       |__Paul  

Program B:

/program-b
  |__2018
       |__Chris Martin
       |__Jonny Buckland
  |__2017
  |__2016
       |__Florence
       |__The Machine  

Answer 1

Here's a good tutorial on how to achieve this: https://straightupcraft.com/articles/how-do-i-only-display-a-list-of-categories-that-have-entries-and-hide-empty-categories

Answer 2

you can use .count() to determine if there is an empty tag:

{% for tag in tags %}
{% set count = craft.entries.section('fellows').relatedTo(category).relatedTo(tag).count() %}
  {% if count > 0 %}
     <h3>{{ tag.slug }} {{ category.title }}</h3>
         {% for entry in craft.entries({
                                relatedTo: [
                                  'and',
                                  { targetElement: category },
                                  { targetElement: tag },
                                  ],
                                  limit: (null),
                                  }) %}
               {% include '_entryblock.twig' %} 
  {% endif %}
{% endfor %}