Fix failure to stake as researcher with expired beacon
Fix failure to stake as researcher with expired beacon

Fixes #525

If a researcher's beacon expired, generate the block as an investor. We
cannot sign a research claim without the beacon key, so this avoids the
issue that prevents a researcher from staking blocks if the beacon does
not exist (it expired or it has yet to be advertised).

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