Fixup tests

Author: danog

tests/Loop/ForeachTest.php

@@ -1027,9 +1027,7 @@ function foo() : void {
                         $arr = [];
 
                         foreach ([1, 2, 3] as $i) {
-                            if (!isset($arr[$i]["a"])) {
-                                $arr[$i]["a"] = 0;
-                            }
+                            $arr[$i]["a"] ??= 0;
 
                             $arr[$i]["a"] += 5;
                         }