Good news: that message is harmless, and it doesn't come from Objo at all.
error messaging the mach port for IMKCFRunLoopWakeUpReliable is written by macOS itself, specifically by the Input Method Kit framework that manages text input. It appears when the active keyboard input source changes, which is exactly what you did when switching from Azerty to Pinyin, and it shows up in the logs of many unrelated Mac apps. Your app and your TextField are unaffected, so you can safely ignore it.
The reason it looked so alarming is Studio's fault. Studio captures everything a running app writes to its output stream, and until now it displayed operating-system lines like this one in the same red it uses for real errors. OS background noise should never look like an Objo error.
I've tracked that here: Show OS console messages in muted grey and add a setting to hide them. Messages from the operating system will appear in a muted grey colour so they can't be mistaken for errors, and a new Show OS messages setting (Settings → Editor, on by default) will let you hide them entirely. In the meantime, the OS Messages button on the console toolbar hides them for the current session.