Unexpected NullPointerException in Elytron tests when init capabilities are missing

If capabilities required for initializing Elytron test cases are missing, a NullPointerException is thrown, instead of printing the error message, since capability failures do not throw an exception. Because Elytron test cases are not run in admin-only mode, these failures are not ignored and result in a subsystem boot failure. References:

• Failure in test case initialization, when subsystem boot fails
• ModelTestKernelServicesImpl.getBootError(), returns a Throwable
• ModelTestModelControllerService.boot() only sets error if one is raised/thrown
• OperationContextImpl.validateCapabilities() creates a logger message but doesn't throw an exception