Update validation of required integer fields with "0" value in ConditionalFieldsFormHelper.php

Closes #3512213

src/ConditionalFieldsFormHelper.php

@@ -589,7 +589,7 @@ class ConditionalFieldsFormHelper {
                 $field = NULL;
               }
 
-              if (empty($input_state)) {
+              if (empty($input_state) && $input_state !== '0') {
                 if (isset($element['widget']['#title'])) {
                   $title = $element['widget']['#title'];
                 }