core: append transactions to the block in GetBlock()

We want to get a full block, so it has to have transactions
inside. Unfortunately our tests were used to this wrong behavior and utilized
completely bogus transactions without data that couldn't be persisted, so fix
that also.

pkg/rpc/server_helper_test.go

@@ -172,14 +172,15 @@ func initBlocks(t *testing.T, chain *core.Blockchain) {
 func makeBlocks(n int) []*core.Block {
 	blocks := make([]*core.Block, n)
 	for i := 0; i < n; i++ {
-		blocks[i] = newBlock(uint32(i+1), newTX(transaction.MinerType))
+		blocks[i] = newBlock(uint32(i+1), newMinerTX())
 	}
 	return blocks
 }
 
-func newTX(t transaction.TXType) *transaction.Transaction {
+func newMinerTX() *transaction.Transaction {
 	return &transaction.Transaction{
-		Type: t,
+		Type: transaction.MinerType,
+		Data: &transaction.MinerTX{},
 	}
 }