Move mixInLength below error handling

beacon-chain/cache/depositsnapshot/deposit_tree.go

@@ -148,10 +148,10 @@ func (d *DepositTree) getRoot() [32]byte {
 //nolint:unused
 func (d *DepositTree) pushLeaf(leaf [32]byte) error {
 	var err error
-	d.mixInLength++
 	d.tree, err = d.tree.PushLeaf(leaf, DepositContractDepth)
 	if err != nil {
 		return err
 	}
+	d.mixInLength++
 	return nil
 }