using JUCE 3.1.1 on linux
when ComboBox dropdown options are dismissed i see the following error in terminal:
ERROR: X returned BadMatch (invalid parameter attributes) for operation X_ConfigureWindow
this occurs only if the dropdown options are dismissed by clicking elsewhere (not selecting an option) - the ESC key similarly dismisses the dropdown but does not produce ther error - this is reproducable 100% of the time
however there seems to be no ill effects of this