BUG: Fix segfault on mesa.
BUG: Fix segfault on mesa.

Can't query for OpenGL extensions outside of render.

Change-Id: I2fc1210a39ec0205f94f9fd25f499b2de5fcd5fe

mspark93/VTK,candy7393/VTK,keithroe/vtkoptix,hendradarwin/VTK,mspark93/VTK,berendkleinhaneveld/VTK,demarle/VTK,cjh1/VTK,msmolens/VTK,collects/VTK,demarle/VTK,johnkit/vtk-dev,daviddoria/PointGraphsPhase1,hendradarwin/VTK,aashish24/VTK-old,sankhesh/VTK,johnkit/vtk-dev,hendradarwin/VTK,cjh1/VTK,collects/VTK,mspark93/VTK,ashray/VTK-EVM,demarle/VTK,keithroe/vtkoptix,jmerkow/VTK,spthaolt/VTK,spthaolt/VTK,SimVascular/VTK,keithroe/vtkoptix,candy7393/VTK,berendkleinhaneveld/VTK,gram526/VTK,spthaolt/VTK,sankhesh/VTK,jmerkow/VTK,demarle/VTK,keithroe/vtkoptix,daviddoria/PointGraphsPhase1,demarle/VTK,demarle/VTK,sumedhasingla/VTK,ashray/VTK-EVM,gram526/VTK,sankhesh/VTK,collects/VTK,ashray/VTK-EVM,cjh1/VTK,sankhesh/VTK,jmerkow/VTK,gram526/VTK,jmerkow/VTK,biddisco/VTK,biddisco/VTK,SimVascular/VTK,berendkleinhaneveld/VTK,johnkit/vtk-dev,cjh1/VTK,berendkleinhaneveld/VTK,sumedhasingla/VTK,jmerkow/VTK,biddisco/VTK,gram526/VTK,keithroe/vtkoptix,msmolens/VTK,aashish24/VTK-old,hendradarwin/VTK,keithroe/vtkoptix,sankhesh/VTK,spthaolt/VTK,candy7393/VTK,gram526/VTK,gram526/VTK,sumedhasingla/VTK,sumedhasingla/VTK,spthaolt/VTK,sumedhasingla/VTK,jmerkow/VTK,candy7393/VTK,SimVascular/VTK,mspark93/VTK,msmolens/VTK,sumedhasingla/VTK,SimVascular/VTK,johnkit/vtk-dev,gram526/VTK,candy7393/VTK,ashray/VTK-EVM,demarle/VTK,daviddoria/PointGraphsPhase1,sankhesh/VTK,ashray/VTK-EVM,johnkit/vtk-dev,candy7393/VTK,ashray/VTK-EVM,gram526/VTK,msmolens/VTK,johnkit/vtk-dev,msmolens/VTK,spthaolt/VTK,msmolens/VTK,biddisco/VTK,hendradarwin/VTK,ashray/VTK-EVM,demarle/VTK,msmolens/VTK,SimVascular/VTK,keithroe/vtkoptix,daviddoria/PointGraphsPhase1,collects/VTK,sankhesh/VTK,collects/VTK,mspark93/VTK,sankhesh/VTK,aashish24/VTK-old,berendkleinhaneveld/VTK,SimVascular/VTK,cjh1/VTK,spthaolt/VTK,aashish24/VTK-old,biddisco/VTK,SimVascular/VTK,aashish24/VTK-old,candy7393/VTK,daviddoria/PointGraphsPhase1,mspark93/VTK,biddisco/VTK,biddisco/VTK,johnkit/vtk-dev,ashray/VTK-EVM,jmerkow/VTK,aashish24/VTK-old,msmolens/VTK,keithroe/vtkoptix,hendradarwin/VTK,hendradarwin/VTK,mspark93/VTK,berendkleinhaneveld/VTK,cjh1/VTK,sumedhasingla/VTK,sumedhasingla/VTK,jmerkow/VTK,candy7393/VTK,daviddoria/PointGraphsPhase1,mspark93/VTK,SimVascular/VTK,collects/VTK,berendkleinhaneveld/VTK