Simplify front-end error-clearing logic.

undercover/templates/writing.jinja2

@@ -32,7 +32,7 @@
 
     const clearErrors = () => {
       const e = document.getElementById('letter_errors')
-      e.parentNode.removeChild(e)
+      e?.parentNode.removeChild(e)
     }
   </script>
 {% endblock head %}
@@ -106,11 +106,7 @@
       <a href="javascript:void(0)"
          class="wipe up-wipe"
          style="margin-bottom: 1em;"
-        {% if letter_errors %}
-          onclick="clearErrors();document.getElementById('letter-form').submit()"
-        {% else %}
-          onclick="document.getElementById('letter-form').submit()"
-        {% endif %}
+         onclick="clearErrors();document.getElementById('letter-form').submit()"
       >Generate PDF</a>
     </div>
   </form>