prevent crash if the pending vectors queue contains the same item multiple times (#990)
prevent crash if the pending vectors queue contains the same item multiple times (#990)


fassadlr/StratisBitcoinFullNode,mikedennis/StratisBitcoinFullNode,stratisproject/StratisBitcoinFullNode,bokobza/StratisBitcoinFullNode,bokobza/StratisBitcoinFullNode,bokobza/StratisBitcoinFullNode,mikedennis/StratisBitcoinFullNode,Aprogiena/StratisBitcoinFullNode,Aprogiena/StratisBitcoinFullNode,quantumagi/StratisBitcoinFullNode,Neurosploit/StratisBitcoinFullNode,fassadlr/StratisBitcoinFullNode,bokobza/StratisBitcoinFullNode,Aprogiena/StratisBitcoinFullNode,mikedennis/StratisBitcoinFullNode,mikedennis/StratisBitcoinFullNode,stratisproject/StratisBitcoinFullNode,Neurosploit/StratisBitcoinFullNode,Neurosploit/StratisBitcoinFullNode,quantumagi/StratisBitcoinFullNode