fix: optimization: PVS-Studio warning V832

It's better to use '= default;' syntax instead of empty constructor and destructor body.
Using '= default;' can help the compiler generate more optimal code.

Reported by: PVS-Studio

Signed-off-by: Vyacheslav Ivanov <islavaivanov76@gmail.com>

src/frontend/ContentGfxCache.cpp

@@ -38,8 +38,7 @@ ContentGfxCache::ContentGfxCache(const Content* content, Assets* assets) : conte
     }
 }
 
-ContentGfxCache::~ContentGfxCache() {
-}
+ContentGfxCache::~ContentGfxCache() = default;
 
 const Content* ContentGfxCache::getContent() const {
     return content;