This is the same issue:
I worked around this by compiling my own modified indicator applet without hotkey.
I didn’t have the same success as the other poster who mentioned using regular Indicator Applet instead, but if you want to try, you’d right-click the indicator and unlock it from the panel. Then untick “Lock to panel,” right-click again and choose “remove from panel,” then right-click the blank area, Add To Panel…, and add the “Indicator Applet”.
If something goes wrong and your panel is all messed up, either do a mate-panel --reset in Terminal, or go to MATE Tweak and reload one of the panel layouts.