Icon address gets corrupted

I’m using https and initially the plus and minus icons appeared fine. Then, after editig the sample style they were gone: The “https://mydomain.com” prefix to the address was doubled up in the page output, so could not be found. I deleted the “https://mydomain.com” prefix from the default icon addresses in the options, but the plugin complains I can’t have both a gradient and an icon (yet it then works). A relative URL is quite correct, and more portable. Just check for it being a valid URL – could be relative, or even to another web address.
Otherwise a really great plugin, many thanks und kudos!
Tim