options.twig sample code:
................
{# Hide empty answers at print overview #}
<div class='col-sm-12 col-md-4'>
<div class='form-group row'>
<label for='simple_edit_options_hideempty' class='control-label'> {{ gT("Hide un-checked items at print overview") }} </label>
<div class='col-sm-12'>
<div class="btn-group" data-toggle="buttons">
<label class="btn btn-default">
<input type='radio' name='hideempty' value='on' class='selector_option_radio_field simple_edit_options_hideempty ' data-id='hideempty'/>
{{ gT("Yes") }}
</label>
<label class="btn btn-default">
<input type='radio' name='hideempty' value='off' class='selector_option_radio_field simple_edit_options_hideempty ' data-id='hideempty'/>
{{ gT("No") }}
</label>
{# If this is a root template setting, don't show the inherit button #}
{% if templateConfiguration.sid is not empty or templateConfiguration.gsid is not empty %}
<label class="btn btn-default">
<input type='radio' name='hideempty' value='inherit' class='selector_option_radio_field simple_edit_options_hideempty ' data-id='hideempty'/>
{{ gT("Inherit") }}
</label>
{% endif %}
</div>
</div>
</div>
</div>
..........

config.xml new setting:
....
<showpopups>1</showpopups>
<fixnumauto>off</fixnumauto>
<!-- 2020-06-26 Marcel Minke: New print option setting -->
<hideempty>on</hideempty>
</options>
<!-- Engine configuration is the very same as vanilla -->
</config>

Error message:
Recoverable error
Object of class stdClass could not be converted to string

/var/www/vhosts/my-survey.host/fma.my-survey.host/ls/application/core/LSETwigViewRenderer.php(512)

500 $showxquestions = Yii::app()->getConfig('showxquestions');
501 $aDatas["aSurveyInfo"]['bShowxquestions'] = ($showxquestions == 'show' || ($showxquestions == 'choose' && !isset($aDatas['aSurveyInfo']['showxquestions'])) || ($showxquestions == 'choose' && $aDatas['aSurveyInfo']['showxquestions'] == 'Y'));
502
503
504 // NB: Session is flushed at submit, so sid is not defined here.
505 if (isset($SESSION['survey'.$aDatas['aSurveyInfo']['sid']]) && isset($SESSION['survey'.$aDatas['aSurveyInfo']['sid']]['totalquestions'])) {
506 $aDatas["aSurveyInfo"]['iTotalquestions'] = $SESSION['survey'.$aDatas['aSurveyInfo']['sid']]['totalquestions'];
507 }
508
509 // Add the survey theme options
510 if ($oTemplate->oOptions) {
511 foreach ($oTemplate->oOptions as $key => $value) {
512 $aDatas["aSurveyInfo"]["options"][$key] = (string) $value;
513 }
514 }
515 } else {
516 // Add the global theme options
517 $oTemplateConfigurationCurrent = Template::getInstance($oTemplate->sTemplateName);
518 $aDatas["aSurveyInfo"]["options"] = isJson($oTemplateConfigurationCurrent['options'])?(array)json_decode($oTemplateConfigurationCurrent['options']):$oTemplateConfigurationCurrent['options'];
519 }
520
521 $aDatas = $this->fixDataCoherence($aDatas);
522
523 return $aDatas;
524 }