reduce segfaults on shader compile failure
When a shader program fails to compile often the application would crash because code assumed that the program was created. The shader compilation error messages often were hard to obtain as the segault kills the output window. This topic catches many places where the program was assumed to exists and makes them not crash. It was developed by modifying the shader cache to always fail when building a shader and then running the VTK tests to see if anything crashed. Lots did. With this topic at least ctest -R OpenGL2 ctest -R RenderingCore ctest -R Chart all work without segaulting even when the shader fails to compile. This makes catching the shader compilation error messages lots easier and of course less chance of an application segfaulting as opposed to gracefully reporting an error.
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