first of all, you should use autosend:true (or just not use autosend:false) to start uploading after selecting an image from the file system.
Secondly, you should check what is returned by the POST request as exactly this response comes into onFileUpload event.
And here we encounter the problem that Databoom actually returns no response! You can see it even when trying to upload the file in the admin area in the Files tab.
Such a situation (no response) is interpreted as upload error by Webix Uploader and it issues the onFileUploadError event.
But there can be a workaround. You can catch the onDataUpdate event of the uploader file storage and take file info from handler parameters:
view:"uploader",
"files->onDataUpdate":function(id, item){
//item - context, file, id, name, size, sizetext, status, type
var id = item.context.rowid;
var row = $$("people").getItem(id);
row.photo = item.name;
$$("people").updateItem(id, row);
}