SteamVR: Several thumbnails fail to display in several menus within SteamVR Dashboard overlay.

[KWS-Compat]

SteamVR fails to display thumbnail images in several instances on the SteamVR Dashboard. The first instance takes place when SteamVR Home is booted up, the user can observe the application's thumbnail is missing on both the compositor and the dashboard (see attachment 1). The second instance occurs on three submenus (Environment, Base Station, Controller) within the Customize tab of SteamVR Settings. If the user already has some workshop items downloaded for each of these categories, their thumbnails will not show up and it appears as if there's nothing on these submenus (see attachment 2). Moving the controller's pointer to where the content is supposed to be, the user will see the thumbnail borders for each item.

Repro Steps:

1. Launch SteamVR.
2. While SteamVR Home is booting up, observe that the application's thumbnail is not loaded.
3. Open SteamVR Dashboard.
4. Navigate to the Settings, then Customize tab.
5. Select any of the affected submenus (Environment, Base Station, Controller).
6. Download workshop content for each submenu if there's none.
7. Once downloaded, return to these submenus. Observe that the thumbnails for downloaded content fail to display and the whole menu appear as if there's nothing on them.

Repro Rate: 5/5

Expected Result: SteamVR Home's thumbnail to be displayed properly upon launched. And workshop items' thumbnails within the Customize menu should show up after downloaded. Actual Result: SteamVR Home thumbnails and Custom workshop item's thumbnails fail to display.

Observed Configurations: Observed on CPU: Intel i7-7700K, AMD Ryzen 7 1700, AMD Ryzen 7 2700 Observed on GPU: Nvidia GTX 980 TI, Nvidia GTX Titan X, AMD Radeon R9 Fury Observed on HMD: HTC Vive, HTC Vive Pro, Oculus Rift

Builds: SteamVR Live Build: 1.6.10 SteamVR Beta Build: 1.6.10

[KWS-Compat]

Issue still occurs as of SteamVR Beta Version 1.7.15