Here is the bug URL
I got the solution from there as well, as this was an extremely annoying bug for me and I consider it a FATAL One!
Open a terminal and run the following command:
"nohup env GDK_NATIVE_WINDOWS=1 gnome-panel --replace &"
"nohup": To run the command independent from the terminal, so as not to cancel the action if the terminal is closed.
'&': Must be put at the end of a command run using "nohup" to run it in the background and avoid canceling the command.
The above command will restart the "gnome-panel" and you'll find that the bug disappeared.
I haven't restarted my machine yet to know whether this command is persistent or not (I think not), but anyway it can be easily put in the session startup if it's not.
Thanks go to "schuetza" who suggested this nice workaround on the original bug report.