Emscripten_SetWindowFullscreen: Fix crash due to uninitialized EmscriptenFullscreenStrategy members

(cherry picked from commit 7b74e2eeb8f435b1beba5945ad605b7b0942f8fb)

src/video/emscripten/SDL_emscriptenvideo.c

@@ -342,6 +342,7 @@ static void Emscripten_SetWindowFullscreen(_THIS, SDL_Window *window, SDL_VideoD
             SDL_bool is_desktop_fullscreen = (window->flags & SDL_WINDOW_FULLSCREEN_DESKTOP) == SDL_WINDOW_FULLSCREEN_DESKTOP;
             int res;
 
+            SDL_zero(strategy);
             strategy.scaleMode = is_desktop_fullscreen ? EMSCRIPTEN_FULLSCREEN_SCALE_STRETCH : EMSCRIPTEN_FULLSCREEN_SCALE_ASPECT;
 
             if (!is_desktop_fullscreen) {