ptr.deleteList does not return when trying to delete something that's not a list.

[cristianvasquez]

ptr.deleteList does not return when trying to delete something that's not a list.

Example:

const parse = require('./support/parse.js')
const rdf = require('./support/factory')

const data = `
<http://buggy> <https://cube.link/view/argument> "2019-01-01T23:00:00.000Z"^^<http://www.w3.org/2001/XMLSchema#dateTime> .
`

async function main () {
  const cf = await parse(data)
  const ptr = cf.node(rdf.namedNode('http://buggy'))
  ptr.deleteList(rdf.namedNode('https://cube.link/view/argument'))
}

main()

Perhaps some checking is required?

[cristianvasquez]

Fix at #68