test in test must still open own error handler

Author: mvorisek

src/Runner/ErrorHandler.php

@@ -163,13 +163,7 @@ public function enable(): void
             return;
         }
 
-        $oldErrorHandler = set_error_handler($this);
-
-        if ($oldErrorHandler !== null) {
-            restore_error_handler();
-
-            return;
-        }
+        set_error_handler($this);
 
         $this->enabled = true;