Open infinite window of Preferences Pane in Cocoa app when using segue
<p>I want to open a preference pane in my Cocoa app when an user taps the <code>Preferences...</code> menu or typing <kbd>⌘</kbd>+<kbd>,</kbd>. So I connected from the preferences menu item to the window controller in storyboard as a <code>show</code> segue.</p>

<p>However, while this opens the preference pane when an user taps <code>Preferences...</code>, if the user taps the menu item again before closing the pane, another pane is going to be launched and displayed on the screen.</p>

<p>I want to have only one preference pane in my screen but how can I do that? I want to set it up only on storyboard and avoid coding that makes the nest of nest of boring menu items...</p>