Improve error handling in screen initialization

After the struct screen is initialized, the window, the renderer and the
texture are necessarily valid, so there is no need to check in
screen_destroy().

app/src/screen.c

@@ -270,7 +270,7 @@ screen_init_rendering(struct screen *screen, const char *window_title,
                                           SDL_RENDERER_ACCELERATED);
     if (!screen->renderer) {
         LOGC("Could not create renderer: %s", SDL_GetError());
-        screen_destroy(screen);
+        SDL_DestroyWindow(screen->window);
         return false;
     }
 
@@ -318,7 +318,8 @@ screen_init_rendering(struct screen *screen, const char *window_title,
     screen->texture = create_texture(screen);
     if (!screen->texture) {
         LOGC("Could not create texture: %s", SDL_GetError());
-        screen_destroy(screen);
+        SDL_DestroyRenderer(screen->renderer);
+        SDL_DestroyWindow(screen->window);
         return false;
     }
 
@@ -339,15 +340,9 @@ screen_show_window(struct screen *screen) {
 
 void
 screen_destroy(struct screen *screen) {
-    if (screen->texture) {
-        SDL_DestroyTexture(screen->texture);
-    }
-    if (screen->renderer) {
-        SDL_DestroyRenderer(screen->renderer);
-    }
-    if (screen->window) {
-        SDL_DestroyWindow(screen->window);
-    }
+    SDL_DestroyTexture(screen->texture);
+    SDL_DestroyRenderer(screen->renderer);
+    SDL_DestroyWindow(screen->window);
 }
 
 static void