Hi, I’ve been seeing the same warning for a while now. I’m not an expert, so I can’t tell you if it might affect performance or other issues, but at least in my projects, I haven’t noticed any anomalies beyond this warning.
However, if you want it to stop appearing, there’s an easy solution by adding the following code (line 97) in the file /themes/pro/cornerstone/includes/elements/definitions/map.php if you use Pro, or in /plugins/cornerstone/includes/elements/definitions/map.php if you use X.
Although, if you’re not familiar with the code, I’d recommend not touching it in case an error occurs on your website and you don’t know how to fix it. Also, once Theme.co releases a new version, the file will be overwritten, and the warning will reappear unless they add the fix in the new version.
Cheers!