Console error: Promised response from onMessage listener […] went out of scope

[rugk]

trafficstars

Via about:debugging I found that this add-on yields these errors really much:

19:12:09.847 Error: Promised response from onMessage listener at onMessage@moz-extension://52e61681-a517-493a-98b8-54ae02c28680/background.js:132:9 went out of scope undefined
19:12:09.851 Error: Promised response from onMessage listener at @moz-extension://9ac43c25-d910-40f3-80f6-a9fa860c3e04/background/init.js:77:1 went out of scope  undefined
19:12:09.851 Error: Promised response from onMessage listener at onMessage@moz-extension://52e61681-a517-493a-98b8-54ae02c28680/background.js:132:9 went out of scope

• System OS: (e.g., Fedora 27)
• Firefox version: (e.g., Firefox 59)
• Textarea Cache version: (e.g., 3.19.5)