Simplify not working with matrix multiplication?

Shouldn't the following produce the same result?

```js
import * as math from 'mathjs'

let scope = {
A: math.matrix([
[1, 2],
[3, 4],
]),
v: math.matrix([5, 6]),
}

const r0 = math.evaluate('A * v', scope)
console.log('Evaluate:', r0) // Evaluate: DenseMatrix {_data: [17, 39]}

//const A = new math.SymbolNode('A')
//const v = new math.SymbolNode('v')
//const expr = new math.OperatorNode('*', 'multiply', [A, v])
const expr = math.parse('A * v')

const r1 = math.simplify(expr, scope)
console.log('Simplify:', r1) // Simplify: ConstantNode {value: 0}
```

When I run the code, `evaluate` produces the expected output (`[17, 39]`), but `simplify` does not (it instead produces `0` which doesn't seem right).