bug-14538: Remove validation error codes

https://cvs.khronos.org/bugzilla/show_bug.cgi?id=14538
diff --git a/demos/cube.c b/demos/cube.c
index 608c480..aa74335 100644
--- a/demos/cube.c
+++ b/demos/cube.c
@@ -2308,7 +2308,7 @@
                  "(ICD).\n\nPlease look at the Getting Started guide for "
                  "additional information.\n",
                  "vkCreateInstance Failure");
-    } else if (err == VK_ERROR_INVALID_EXTENSION) {
+    } else if (err == VK_ERROR_EXTENSION_NOT_PRESENT) {
         ERR_EXIT("Cannot find a specified extension library"
                  ".\nMake sure your layers path is set appropriately\n",
                  "vkCreateInstance Failure");