Fix code in swap chain recreation chapter being out of sync with example code file

Overv · Overv · commit 16dabc1ebf9f · 2018-07-22T14:01:59.000+02:00
diff --git a/03_Drawing_a_triangle/04_Swap_chain_recreation.md b/03_Drawing_a_triangle/04_Swap_chain_recreation.md
@@ -95,7 +95,11 @@ void cleanup() {
     vkDestroyCommandPool(device, commandPool, nullptr);
 
     vkDestroyDevice(device, nullptr);
-    DestroyDebugReportCallbackEXT(instance, callback, nullptr);
+
+    if (enableValidationLayers) {
+        DestroyDebugReportCallbackEXT(instance, callback, nullptr);
+    }
+
     vkDestroySurfaceKHR(instance, surface, nullptr);
     vkDestroyInstance(instance, nullptr);
 
