Issue#3379993: Resolving deprecation issue with coalescing operator.

views/theme/views_views_json_style.theme.inc

@@ -56,10 +56,7 @@ function template_preprocess_views_views_json_style_simple(&$vars) {
           }
           else {
             $content = $plaintext_output ? strip_tags(html_entity_decode($field->content, ENT_QUOTES)) : $field->content;
-
-            if (!empty($content)) {
-              $content = mb_check_encoding($content, 'UTF-8') ? $content : utf8_encode($content);
-            }
+            $content = $content ?? mb_check_encoding($content, 'UTF-8') ? $content : utf8_encode($content);
           }
         }
         else {