refactored rule execution. [skip ci]

framework/rbac/DbManager.php

@@ -655,9 +655,6 @@ class DbManager extends Manager
      */
     public function getRule($name)
     {
-        if ($name === null) {
-            return null;
-        }
         $query = new Query;
         $query->select(['data'])->from($this->ruleTable)->where(['name' => $name]);
         $row = $query->createCommand($this->db)->queryOne();

framework/rbac/Manager.php

@@ -151,6 +151,9 @@ abstract class Manager extends Component
      */
     public function executeRule($ruleName, $params, $data)
     {
+        if ($ruleName === null) {
+            return true;
+        }
         $rule = $this->getRule($ruleName);
         if ($rule instanceof Rule) {
             return $rule->execute($params, $data);

framework/rbac/PhpManager.php

@@ -628,7 +628,7 @@ class PhpManager extends Manager
      */
     public function getRule($name)
     {
-        return $name !== null && isset($this->_rules[$name]) ? $this->_rules[$name] : null;
+        return isset($this->_rules[$name]) ? $this->_rules[$name] : null;
     }
 
     /**