2D viewer issue with empty ensembles

[HansKallekleiv]

Issue when using one or more cases without surface metadata and a case with surface metadata.
Settings component is stuck in a loading state and/or no data is visualized in view.

To reproduce infinite loading spinner:

1. Load two ensembles without surfaces (e,g, top two JS cases (non-keep))
2. Add 2d viewer with realization surface
3. Surface settings should render correctly indicating no data
4. Switch to the other ensemble.
5. Note the infinite loading spinner

To reproduce no data visualized:

1. Load an ensemble without surfaces and one ensemble with surfaces
2. Visualize a surface from the working ensemble
3. Switch back and forth between ensembles
4. Note that the surface is no longer visualizing (until another surface is selected)