Fixed crash when halide_set_cl_context is not called
Fixed crash when halide_set_cl_context is not called


Former-commit-id: f2c8a81a511769650f016f72bfb11f45a6e73fc9
Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide