correctly fix invalid read from pvoc array

[Jan200101]

follow up to #14 after I had been urged to look into this more

the real problem was caused by prplnt, the integer used to define the size of the pvoc array, being off by 3 causing an invalid read I recreated the environment that caused the crash from #14 and couldn't replicate anymore with this fix

the value of prplnt could have been intentional considering the place where its used increments by 3 every iteration

I came to the wrong conclusion before because I was debugging the rpm packaged which compiled with -O2