Change from NULL to nullptr for modern usage.
Change from NULL to nullptr for modern usage.

Git-Jiro/Gridcoin-Research,gridcoin/Gridcoin-Research,caraka/gridcoinresearch,Git-Jiro/Gridcoin-Research,caraka/gridcoinresearch,theMarix/Gridcoin-Research,gridcoin/Gridcoin-Research,theMarix/Gridcoin-Research,caraka/gridcoinresearch,gridcoin/Gridcoin-Research,Git-Jiro/Gridcoin-Research,caraka/gridcoinresearch,Git-Jiro/Gridcoin-Research,theMarix/Gridcoin-Research,theMarix/Gridcoin-Research,Git-Jiro/Gridcoin-Research,theMarix/Gridcoin-Research,caraka/gridcoinresearch,gridcoin/Gridcoin-Research,caraka/gridcoinresearch,gridcoin/Gridcoin-Research,theMarix/Gridcoin-Research,gridcoin/Gridcoin-Research