Fix unexpected breaking change

src/MerkleTree.ts

@@ -531,7 +531,13 @@ export class MerkleTree extends Base {
     const proof = []
 
     if (!Number.isInteger(index)) {
-      index = this._bufferIndexOf(this.leaves, leaf, this.sortLeaves)
+      index = -1
+
+      for (let i = 0; i < this.leaves.length; i++) {
+        if (Buffer.compare(leaf, this.leaves[i]) === 0) {
+          index = i
+        }
+      }
     }
 
     if (index <= -1) {

test/MerkleTree.test.js

@@ -1291,3 +1291,13 @@ test('complete option with incompatible options', t => {
   )
 })
 
+test('simple bad proof', t => {
+  t.plan(2)
+
+  const leaves = ['d', 'e', 'f']
+  const tree = new MerkleTree(leaves)
+
+  const proof = tree.getHexProof(leaves[0])
+  t.equal(proof.length, 1)
+  t.equal(proof[0], '0xe3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855')
+})