Misc. bug: hipGraph causes a crash in hipGraphDestroy

First encountered when testing https://github.com/ggml-org/llama.cpp/pull/11867, but this is a problem in master too. Debugged to a bug in rocm-clr: https://github.com/ROCm/clr/issues/138

This issue tracks that currently non-defaults builds with GGML_HIP_GRAPHS=On are unreliable and will be closed when the corresponding upstream bug is addressed.