fix: not checking if actors have datasets.

[germa89]

As the title.

Close #208 by implementing our own meshes method.

[germa89]

This method wasn't tested, so I leave it up to @AlejandroFernandezLuces if he wants to add a tests or not.

I guess it should not be needed since the slicer (MeshSliderWidget) does not seem to be much exposed??

[germa89]

The issue has been fixed upstream in pyvista/pyvista#6860.
It is just yet not published.

[AlejandroFernandezLuces]

This method wasn't tested, so I leave it up to @AlejandroFernandezLuces if he wants to add a tests or not.

I guess it should not be needed since the slicer (MeshSliderWidget) does not seem to be much exposed??

Since this is temporary I think we don't need to test it. Let's merge this if you need it and we can remove it when bumping the next PyVista version.