Fixed crash if GetRectDisplayIndex() is called before SDL_VideoInit()

src/video/SDL_video.c

@@ -1122,6 +1122,7 @@ static int GetRectDisplayIndex(int x, int y, int w, int h)
     center.x = x + w / 2;
     center.y = y + h / 2;
 
+    if (_this) {
         for (i = 0; i < _this->num_displays; ++i) {
             SDL_Rect display_rect;
             SDL_GetDisplayBounds(i, &display_rect);
@@ -1143,6 +1144,7 @@ static int GetRectDisplayIndex(int x, int y, int w, int h)
                 closest_dist = dist;
             }
         }
+    }
 
     if (closest < 0) {
         SDL_SetError("Couldn't find any displays");