Non blocking plt::show(false) does not work under Windows

I tried it with Python2.7 and Python3 in Visual Studio 2019. In both cases the plot window freezes if I use `plt::show(false);`. Just `plt::show();` works for me.
E.g. the following does not work:

```
    std::vector<float> test_values = { 1.0f, 3.0f, 2.0f };
    plt::plot(test_values);
    plt::show(false);
    while (1)
    {

    }
```