BUGFIX: RuntimeSequenceHttpRequestHandler::$httpRequest must not be accessed before initialization

[mhsdesign]

if in testing context the throwable storage is invoked the default $requestInformationRenderer will cause getHttpRequest to be called

Now there is a null check, but its useless with php strict defined properties:

Typed property Neos\Flow\Testing\RequestHandler\RuntimeSequenceHttpRequestHandler::$httpRequest must not be accessed before initialization

Either we must use isset or default initialise the value to null

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