Make media assets show a placeholder thumbnail when the image is missing. This can happen if the upload is still processing, or if the media asset's image was expunged, or if the asset failed during upload (usually because of some temporary network failure when trying to distribute thumbnails to the backend image servers). Fixes a problem where new images on the My Uploads or All Uploads pages could have broken thumbnails if they were still in the uploading phase.
Components
Components are used to encapsulate common UI widgets used throughout the site. This includes things like comments, tag lists, post thumbnails, paginators, and other things used repeatedly throughout the site. Components encapsulate a widget's HTML, CSS, and Javascript together so that all the code for a component is in a single place.
This uses the ViewComponent library.
Components are similar in concept to React components.