**What?**

A Vue warning that `ide_status_bar` sent a `Boolean` to a `String`
property (`img-src).

**What was the fix?**

Previously, `latestPipeline` could be one of the following values:

|          |        |
|----------|--------|
| `null`   | The pipeline hasn't loaded yet |
| `false`  | The pipeline has loaded, but nothing was returned. |
| `Object` | The piepline has loaded. |

Giving a semantic meaning to different falsey values hurts
maintainability. This commit fixes the above problem by removing the
`false` value and introducing a `hasLoadedPipeline` state property.