Fix combination of (int) and ??

(int) has higher precedence as ?? and that means the array key is always
casted first and the error suppression part of ?? cannot work

https://www.php.net/manual/en/language.operators.precedence.php

Change-Id: Iee7dc9297c0745ce48295f637a7591ce9385aa4d

includes/changes/ChangesList.php

@@ -752,7 +752,7 @@ class ChangesList extends ContextSource {
 				$user = new UserIdentityValue(
 					(int)$rc->mAttribs['rc_user'],
 					$rc->mAttribs['rc_user_text'],
-					(int)$rc->mAttribs['rc_actor'] ?? 0
+					(int)( $rc->mAttribs['rc_actor'] ?? 0 )
 				);
 				$revRecord->setUser( $user );