Minor changes in derived events to support PAPI_NULL. Shouldn't change results, which, BTW, work on Pentium 4 for an artificial derived event.
Minor changes in derived events to support PAPI_NULL.
Shouldn't change results, which, BTW, work on Pentium 4
for an artificial derived event.

pyrovski/papi,arm-hpc/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,arm-hpc/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi