Add support for empty strinngs in SetInputArrayToProcess.

SetInputArrayToProcess ignored empty strings (treating them same as NULL
strings). This behavior makes it impossible to pick arrays that have no
names. Fixing SetInputArrayToProcess to not ignore empty strings. Also
added a check in GetInputArrayToProcess to handle the case where no
array association was specified.

Change-Id: I3c3a9017ea014c2b8f844133956add72c1cf3e6d
Additional baseline for TestAreaSelections

Change-Id: I3d57c5e00e7ecd90e1ed87e232ece26deb237a07
Merge topic '14258-remote-polyhedra' into pv-master

c8bec1f2 Handle polyhedra in vtkUnstructuredGridWriter.
42b0733e Process facestream in vtkExtractUnstructuredGridPiece::RequestData.
Merge topic 'std_string_ostream_passthrough' into pv-master

c78a1e6a Revert "Pass std::strings through the OStreamWrapper."
c49b9c19 Pass std::strings through the OStreamWrapper.
Merge topic '14615-disable-FPFB' into pv-master

f61c11bc Add new baseline for rendering without floating point buffers.
f521f415 Return early if ProjectedTetrahedra volume rendering is unsupported.
16368b4d Disable FP frame buffer when GL_ARG_texture_float is not present.
Merge topic 'catalyst-web-interactive-composite' into pv-master

eef18179 Merge topic 'catalyst-web-composite' into master
b4f486ff Improve web compositing for dynamic interaction
3df199ea Merge topic '0014457-ExtractPolyData-PassPoints' into master
dd0222fb Merge topic 'proj-tet-baseline' into master
73431db6 Rendering/Volume: Convert new baseline to ExternalData content link
2ee357be Merge topic 'fix-CMP0025-CMP0042-warnings' into master
86c8c55d Merge topic 'proj-tet-baseline' into master
0e07b099 Add new baseline for dashlin1.
075df487 Merge topic 'ensight_binary_time_caching' into master
2ad9f474 Set CMake Policies CMP0025 and CMP0042 as necessary
3a04542c Examples: Set required CMake version and policies before project()
59836055 Refactor top-level CMake Policy settings as loop
08df7a88 Accelerators/Dax: Remove extra call to cmake_minimum_required
ee1c7530 vtkhdf5: Remove extra calls to cmake_minimum_required
5e7a8970 Merge topic '14258-remote-polyhedra' into master
d208c644 Merge topic 'Delaunay3D-Alpha-0014050' into master
...
Merge topic 'enable_subclassing' into pv-master

59b7ad11 Make it possible to override ClampPos.
Merge remote-tracking branch 'pvvtk/pv-master' into HEAD

* pvvtk/pv-master:

Change-Id: Ife0ad531a35dda3d4183608791792e0d80892de9
Merge topic 'support_empty_arrays' into master

c4c8ce83 Add support for empty strinngs in SetInputArrayToProcess.
Merge topic 'TestAreaSelections' into master

0d980664 Additional baseline for TestAreaSelections