The number of responses resulting in the Pull is not of the expected length when using BatchRequest

#### Description:

When using `BatchRequest`s to make concurrent requests, the number of responses is both inconsistent and wrong.

#### How to replicate:

Use the test file in https://github.com/BHoM/HTTP_Toolkit/pull/12
Switch the toggle on and off a couple of times and check the number of elements that the `Pull` outputs. It will not be stationary.

#### Expected behaviour:

If 50 requests are used as input, 50 responses should be returned as output. Some of them can be `null`