cocoa: Convert popup window coordinates to global when adjusting the pointer offset

Fixes a regression in 958c4cbf0d

(cherry picked from commit 013844b003)

src/video/cocoa/SDL_cocoawindow.m

@@ -1924,6 +1924,7 @@ static void Cocoa_SendMouseButtonClicks(SDL_Mouse *mouse, NSEvent *theEvent, SDL
         //if ([_data.listener isInFullscreenSpace]) {
             int posx = 0, posy = 0;
             SDL_GetWindowPosition(window, &posx, &posy);
+            SDL_RelativeToGlobalForWindow(window, posx, posy, &posx, &posy);
             SDL_GetGlobalMouseState(&x, &y);
             x -= posx;
             y -= posy;