canvas: Cannot upload files or create folders

When I attempt to upload a file, or create a new folder within the media interface, the file does not appear, and I get a strange gray box at the top right of the screen for about 5-10 seconds:

This happens both when editing a post, as well as when inside the main media interface.

I have noticed that when I attempt to upload a file, a directory named undefined is created inside of /public/storage and the file is inside that new directory. However, it never appears in the web UI.

Here is the output of the system information:

### Begin System Info ###

## Please include this information when requesting technical support ##

SITE_URL:                   www.christiaanconover.com
SITE_IP:                    100.16.90.229
SITE_TIMEZONE:              America/New_York

PHP_VERSION:                7.0.8-0ubuntu0.16.04.2
PHP_MEMORY_LIMIT:           128M
PHP_TIME_LIMIT:             30

DATABASE_CONNECTION:        MYSQL

WEB_SERVER:                 nginx

LAST_INDEX_RUN:             2016-09-29 09:27:49

### End System Info ###