Fixed NSBeep on certain chords.

src/cocoa_window.m

@@ -466,16 +466,14 @@ static int convertMacKeyCode(unsigned int macKeyCode)
     _glfwInputKey(window, convertMacKeyCode([event keyCode]), GLFW_PRESS);
 
     if ([event modifierFlags] & NSCommandKeyMask)
-        [super keyDown:event];
-    else
-    {
+        return;
+
     NSString* characters = [event characters];
     NSUInteger i, length = [characters length];
 
     for (i = 0;  i < length;  i++)
         _glfwInputChar(window, [characters characterAtIndex:i]);
 }
-}
 
 - (void)flagsChanged:(NSEvent *)event
 {