[DI] Improve integration test error handling (#5500)

In case the integration tests times out trying to create the sandbox,
don't also fail trying to remove it (since it doesn't exist).

Author: watson

integration-tests/debugger/utils.js

@@ -79,7 +79,7 @@ function setup ({ env, testApp, testAppSource } = {}) {
   })
 
   after(async function () {
-    await sandbox.remove()
+    await sandbox?.remove()
   })
 
   beforeEach(async function () {