#245665 fix early task exit with empty promptString input

[johnscollins98]

address issue #245665

tested with the following tasks.json file:

{
  "version": "2.0.0",
  "tasks": [
    {
      "command": "echo",
      "label": "echo",
      "args": [
        "${input:test1}",
        "${input:test2}"
      ]
    }
  ],
  "inputs": [
    {
      "id": "test1",
      "type": "promptString",
      "default": "",
      "description": "test1"
    },
    {
      "id": "test2",
      "type": "promptString",
      "default": "",
      "description": "test2"
    }
  ]
}

entering empty strings into the prompts, before my change it ends early after test1 after it goes all the way through to echo both inputs

[meganrogge]

Thanks!