Please file the bug report yourself. You have all of the details about it.

Still carrying out some additional tests before submitting the bug. When selecting theme options for the first time in a new test survey, a message I get six times reads the following (see the screenshot):

Error: Malformed JSON - field files_css must be either a JSON array or the string "inherit". Found "null".

These messages disappear upon saving the (survey) theme options and they do not appear again, however, when checking the logo field on the images tab, it reads:
Inherit [inherited value: invalid:image:theme::files\logo.png]

My guess: this behavior is related to the [wrong] values saved when extending a template and/or saving template options. Does this sound correct?

Just reminding my configuration:
Windows NT WIN-A34LDHDT6H4 6.3 build 9600 (Windows Server 2012 R2 Standard Edition) AMD64
PHP version 7.2.7
Web server software: Microsoft-IIS/8.5
Database driver version: mysqlnd 5.0.12-dev - 20150407 - $Id: 38fea24f2847fa7519001be390c98ae0acafe387 $
LimeSurvey version/build: 5.2.6/211213

 

I am trying to report the bug, but I get the following:

APPLICATION ERROR #plugin_Discord_ERROR_CURL

The request to Discord didn't go through. Check your webhook URL. Also make sure there are no unusual characters in your bot name or bot icon settings. Further details may be printed below this box.

Please use the "Back" button in your web browser to return to the previous page. There you can correct whatever problems were identified in this error or select another action. You can also click an option from the menu bar to go directly to a new section.APPLICATION ERROR #plugin_Discord_ERROR_CURL

The request to Discord didn't go through. Check your webhook URL. Also make sure there are no unusual characters in your bot name or bot icon settings. Further details may be printed below this box.

Please use the "Back" button in your web browser to return to the previous page. There you can correct whatever problems were identified in this error or select another action. You can also click an option from the menu bar to go directly to a new section.

I just found out that the bug has been reported, despite the error message I mentioned before. I am sorry for submitting the same bug for times. I am not familiar with the system. Bugs No. 17808, 17809, and 17811 should be ignored, but I don't know how to delete or cancel them. Issue No. 10810 is OK.

Again, I am sorry for the repeated submission.

I had this error message as well, yesterday, when I played around with the themes. But I currently don't have the time to investigate and just left the theme as is, as I needed the system running today.