Broken prop reference with operator

[knilink]

input

.foo
  width: 1px
  height: -@width

expected:

.foo {
  width: 1px;
  height: -1px;
}

actual:

TypeError: Cannot read property 'map' of undefined

[knilink]

maybe this line

stylus-converter/src/visitor/index.js

Line 569 in 633a00a

 return `${OPEARTION_MAP[op] || op}(${visitExpression(expr)})` 

should be

return `${OPEARTION_MAP[op] || op}(${visitNode(expr)})`

or check undefined in visitExpression