Image Viewer Base throws error when no images or sources are provided

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: master, master-deprecated
• Fix Version/s: master, master-deprecated, 3.0.x, 3.1.x
• Component/s: Image Viewer
• Labels: None
• Git Pull Request: https://github.com/eduardolundgren/alloy-ui/pull/811

1. Remove the images/sources from the Image Viewer Demo or the Image Viewer Base demo
2. Load the modified demo

Expected result:
No images or controls appear and no errors occur.

Actual result:
The prev/next controls appear and a JavaScript error occurs.