Error building with latest VTK

Hi,

I'm encountering the following error when building with the latest VTK from Git (a5d0539). Same error for the latest Mayavi from Git (31578f6) as well as for the one from pip:

```
running build
----------------------------------------------------------------------
Building TVTK classes... terminate called after throwing an instance of 'std::logic_error'
what(): basic_string::_M_construct null not valid
```

Meanwhile, building with the stable VTK v7.0.0 gives the error which is described in issue #395.

VTK itself compiles and imports cleanly.

Any ideas? Thanks!