Fix dynamically instantiated objects when using newWithBracesFilter.

As the test data demonstrates, a dynamically instantiated class would have been incorrectly 'fixed'.

`return new $someObj['class']($someArg['thing']);`
would become
`return new $someObj['class'()]($someArg['thing']);`
which is invalid PHP.

the same applied when no constructor arguments were provided.
We only need the one line here.