"merkle tree is a binary tree" does not automatically imply that it "needs an even number of leaf nodes". Valid binary trees may contain an odd number of leaf nodes.
Merge branch 'develop' of https://github.com/cgodley/bitcoinbook into cgodley-develop
Changing the sentence to 'The merkle tree is a binary tree with an even number of leaf nodes.'
Merge branch 'cgodley-develop' into develop