Use empty() instead of implicit cast.

src/View/Helper/FormHelper.php

@@ -2356,7 +2356,7 @@ class FormHelper extends Helper
             }
             $parts = explode('.', $field);
             $first = array_shift($parts);
-            $options['name'] = $first . ($parts ? '[' . implode('][', $parts) . ']' : '') . $endsWithBrackets;
+            $options['name'] = $first . (!empty($parts) ? '[' . implode('][', $parts) . ']' : '') . $endsWithBrackets;
         }
 
         if (isset($options['value']) && !isset($options['val'])) {