Warning message displays instead of logo on a site in a password protected direc

First of all, congratulations and many thanks to the author for this elegant theme. I really like it.

However, I’m having a bit of a problem now with loading the logo image on it.

I’ve installed this theme on my new website and on a test site in a password protected directory. The logo image loads fine on the non-password protected site but doesn’t load on the password protected one. In the latter case then, instead of the logo image, I get the following warning:

Warning: getimagesize(http://www.[mysubdomain.mydomain].com/wp-content/uploads/2015/07/%5Bmylogo%5D.png): failed to open stream: HTTP request failed! HTTP/1.1 401 Authorization Required in /home/[myusername]/public_html/[mysubdomain]/wp-content/themes/first/inc/template-tags.php on line 17

I’d really like the logo image to appear properly on the test site too, so they’re identical and I can test changes on the test site first before implementing them on the live site. When I take the password protection off, the logo image loads fine, but I get the warning again when I re-enable the password. Would someone please explain why this warning appears instead of my logo image on my password protected site? Also, is there anything that can be done to fix this so the two sites will be same?

Meanwhile, I suspect this might have something to do with the issue raised here:

https://wordpress.org/support/topic/why-logo-image-downloaded-with-php-server?replies=1

With thanks,

Stuart.

P.S. I’m intending on promoting and growing this site and, by way of thanks, intend to have the credit show in the footer.