I got this message for a long span of time in my .xession-errors, spamming it to grow endlessly. And I saw many people asking about theses messages...
So, I found a way to get rid of it
I had an applet call CPU Temperature Indicator which was flagged as "unsafe" in my Cinnamon config. I just deactivate it!
No more messages, finish!
Hope it'll help!
Have a nice day