improved traceability of errors thrown in toString() methods

framework/yii/mail/BaseMessage.php

@@ -45,7 +45,7 @@ abstract class BaseMessage extends Object implements MessageInterface
 		try {
 			return $this->toString();
 		} catch (\Exception $e) {
-			trigger_error($e->getMessage());
+			trigger_error($e->getMessage() . "\n\n" . $e->getTraceAsString());
 			return '';
 		}
 	}

framework/yii/widgets/ActiveField.php

@@ -130,7 +130,7 @@ class ActiveField extends Component
 		try {
 			return $this->render();
 		} catch (\Exception $e) {
-			trigger_error($e->getMessage());
+			trigger_error($e->getMessage() . "\n\n" . $e->getTraceAsString());
 			return '';
 		}
 	}