The URL scheme blob: is not supported by the java.net.URL bundled in the OpenJDK as default.
If you want to use the blob:, then you need to configure the java.net.URL class.
The URL scheme data: is not supported as well, and I have ever tried to configure the java.net.URL class to recognize the data: scheme. I was successful. The following post tells what I did:
http://forum.katalon.com/t/enabling-data-url-in-katalon-studio/54146
The same procedure should apply to the blob: scheme as well.