con.content is undefined error

[askabelin]

Hi,
I'm using FF 64.0 + geckodriver 0.23.0.
FF is started with -devtools option and devtools.toolbox.selectedTool is set to netmonitor. Executed JS:

HAR.triggerExport().then(log => {
 console.log(log);
});

HAR files seem to be valid. However, I see a lot of "con.content is undefined" errors in geckodriver log:

Extension error: TypeError: con.content is undefined moz-extension://af990852-cf39-4072-9ad3-75cbb82b48b3/src/background.js 44
[[Exception stack
listener@moz-extension://af990852-cf39-4072-9ad3-75cbb82b48b3/src/background.js:44:11
Current stack
applySafeWithoutClone@resource://gre/modules/ExtensionCommon.jsm:529:133
addListener/asyncWithoutClone/<@resource://gre/modules/ExtensionCommon.jsm:2234:20
]]

Is there an easy way to fix it? Can it affect HAR creation?