Here's another solution to a bug that really really can make YOU think to re-install linux mint from zero if you don't have patience to learn linux. 

I think that this one is one of the worst bugs ever for a new user and I would like to say to Linux Mint developers that this should be solved as soon as possible.

I got this solution after two days of work. 

The problem:

OnLinux Mint Petra

I have configured my menu (yes, removing some icons because I'm minimalist) but for some reason the menu editor failed and I couldn't open it again (No matter how many times I clicked to open it. Simply it doesn't work). I restarted my PC and logged in but it's a surprise when I open my menu: There is no icons. 

Solution:

1) Since there is no icons to open a terminal. I prefer to open another instace (CTRL+ALT+F1).

2) log in (normal user does the work).

3) $ cd                                                                           (ensure that you're on your home folder)

4) $ cd .config/menus/

5) $ rm cinnamon-applications.menu                     (remove this file. Since it's broke, it shoul be blank)

6) log off and return to graphical enviroment (CTRL+ALT+F8).

7) Log out your session or restart your computer.

I hope that it could help you. Don't re-install Linux Mint from zero due to this bug.