How to unhide Titlebar and Frame of Pidgin or any application in linux mint?

I played with the application settings of Pidgin and now Pidgin doesn't have any titlebar and frame. I did this with "Right Click on the title bar>More Actions>Special Application Settings>Appearance & Fixes>Checked No Titlebar and frame. How can I undo this? I tried right clicking the application from the taskbar (since I can't right click it on the application because it has no titlebar) but it doesn't show "More Actions".