FIX: correctly measure size of priority block

(cherry picked from commit bitcoin/bitcoin@c2dd5a3c39)

src/miner.cpp

@@ -754,7 +754,7 @@ void BlockAssembler::addPriorityTxs()
 
             // If now that this txs is added we've surpassed our desired priority size
             // or have dropped below the AllowFreeThreshold, then we're done adding priority txs
-            if (nBlockSize + iter->GetTxSize() >= nBlockPrioritySize || !AllowFree(actualPriority)) {
+            if (nBlockSize >= nBlockPrioritySize || !AllowFree(actualPriority)) {
                 return;
             }