Passing a file path in the "Enter URL" field that doesn't start with "file://" and pressing the Continue button will make the wizard proceed to the "Analyzing installer media." without actually doing anything. The Continue button remains active and clicking it takes me to an empty Review screen. The Create button on the Review screen is clickable, but doesn't seem to do anything.
This only happens if the path points to an existing file, so it seems like there is some parsing/checking going on.

Steps to reproduce:
1. Create a box
2. Pass a valid file path (not URI) as the URL
3. Press Continue
Actual result: Strange things start happening
Expected result: The path should be handled as a file:// URI
Proposed fix: When the URL is not a valid URI, check if it's a path pointing to an existing file, display error otherwise.