renderer: Always use the output size when updating the main view

The main view always reflects the size of the output, so don't use the dimensions of the currently bound render target texture when updating it, or it will reflect an incorrect size when the render target texture is unbound.

(cherry picked from commit 8aa5b97)

Author: Kontrabant

src/render/SDL_render.c

@@ -2573,7 +2573,7 @@ static void UpdateLogicalPresentation(SDL_Renderer *renderer)
     const float logical_h = view->logical_h;
     int iwidth, iheight;
 
-    if (renderer->target) {
+    if (!is_main_view && renderer->target) {
         iwidth = (int)renderer->target->w;
         iheight = (int)renderer->target->h;
     } else {