Deprecated Functionality: explode(): Passing null to parameter #2 ($string)

Replace your code selectedFeaturesRaw = $product->getData($attributeCode);
with
$selectedFeaturesRaw = $product->getData($attributeCode) ?: '';

Finally, your code should look like the following:

public function getEnabled()
{
    return $this->_dataHelper->getEnabled();
}

public function getRenderableAttributes()
{
    if (!$this->getEnabled()) {
        return [];
    }
    $attributeCode = $this->_dataHelper->getAttributeCode();
    $product = $this->getProduct();
    $selectedFeaturesRaw = $product->getData($attributeCode) ?: '';
    $selectedFeaturesSplit = explode(',', $selectedFeaturesRaw);
    $attr = $product->getResource()->getAttribute($attributeCode);
    $selectedFeatures = [];
    foreach ($selectedFeaturesSplit as $selectedFeatureCode) {
        if ($attr->usesSource()) {
            $selectedFeatures[] = $attr->getSource()->getOptionText($selectedFeatureCode);
        }
    }
    if (empty($selectedFeatures)) {
        return [];
    }
    $features = [];
    $searchCriteria = $this->_searchCriteriaBuilder->addFilter('attribute_value', $selectedFeatures, 'in')->create();
    $searchResults = $this->_dataRepository->getList($searchCriteria);
    $features = array_map(function ($feature) {
        return $feature->getData();
    }, $searchResults->getItems());
    return $features;
}

Change below line.

    $selectedFeaturesSplit = explode(',', (string)$selectedFeaturesRaw);