Fix phpcs errors.

src/View/ViewBuilder.php

@@ -171,7 +171,7 @@ class ViewBuilder implements JsonSerializable, Serializable
      */
     public function getVar($name)
     {
-        return isset($this->_vars[$name]) ? $this->_vars[$name] : null;
+        return $this->_vars[$name] ?? null;
     }
 
     /**

src/View/ViewVarsTrait.php

@@ -69,7 +69,7 @@ trait ViewVarsTrait
             $builder->setClassName($viewClass);
         }
 
-        $validViewOptions = isset($this->_validViewOptions) ? $this->_validViewOptions : [];
+        $validViewOptions = $this->_validViewOptions ?? [];
         $viewOptions = [];
         foreach ($validViewOptions as $option) {
             if (property_exists($this, $option)) {