Fix prof_tdata_get() to avoid dereferencing an invalid tdata pointer (when it's PROF_TDATA_STATE_{REINCARNATED,PURGATORY}). Fix prof_tdata_get() callers to check for invalid results besides NULL (PROF_TDATA_STATE_{REINCARNATED,PURGATORY}). These regressions were caused by 602c8e0971160e4b85b08b16cf8a2375aa24bc04 (Implement per thread heap profiling.), which did not make it into any releases prior to these fixes.