Fix genesis block change detection

src/main/java/org/qortal/block/GenesisBlock.java

@@ -147,11 +147,11 @@ public class GenesisBlock extends Block {
 		byte[] signature = calcSignature(blockData);
 
 		// Validate block minter's signature (first 64 bytes of block signature)
-		if (!Arrays.equals(signature, 0, 64, blockData.getMinterSignature(), 0, 64))
+		if (!Arrays.equals(signature, 0, 64, genesisBlockData.getMinterSignature(), 0, 64))
 			return false;
 
 		// Validate transactions signature (last 64 bytes of block signature)
-		if (!Arrays.equals(signature, 64, 128, blockData.getTransactionsSignature(), 0, 64))
+		if (!Arrays.equals(signature, 64, 128, genesisBlockData.getTransactionsSignature(), 0, 64))
 			return false;
 
 		return true;