[6.x] Ensure Application::$terminatingCallbacks are reset on Application::flush()

[markokeeffe]

I recently registered a terminating callback in the constructor of one of my services e.g.

$this->container->terminating(function () {
    $this->doSomething();
});

When I ran my application test suite, the memory usage went crazy. Turns out the event listeners for $terminatingCallbacks weren't being cleared out between tests, causing a memory leak.

This change clears out the $terminatingCallbacks array in the Application::flush() method.

[markokeeffe]

Is there any procedure for merging fixes like this down to older versions? Our application is currently using v5.8 of the framework.

[seriquynh]

The failed test cases aren't related to this PR, I think.

[markokeeffe]

@XuanQuynh I was just looking at that, seems like those same tests are failing for a few builds 🤷‍♂

[GrahamCampbell]

We're aware of the test failures. They are due to a redis serialisation configuration problem in the tests.

[driesvints]

Is there any procedure for merging fixes like this down to older versions? Our application is currently using v5.8 of the framework.

5.8 isn't supported anymore sorry.