[Chain] Prevent FindFork from crashing when pindex is null (Only should happen on reindexing and initial sync).
[Chain] Prevent FindFork from crashing when pindex is null (Only should happen on reindexing and initial sync).

PIVX-Project/PIVX,Darknet-Crypto/Darknet,PIVX-Project/PIVX,PIVX-Project/PIVX,Darknet-Crypto/Darknet,Darknet-Crypto/Darknet,PIVX-Project/PIVX,Darknet-Crypto/Darknet,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,Darknet-Crypto/Darknet,Darknet-Crypto/Darknet,PIVX-Project/PIVX,PIVX-Project/PIVX