fix: material sandbox scene crashes during shutdown (#9325)

samples/material_sandbox.cpp

@@ -191,6 +191,8 @@ static int handleCommandLineArgments(int argc, char* argv[], Config* config) {
 }
 
 static void cleanup(Engine* engine, View*, Scene*) {
+    g_meshSet.reset(nullptr);
+
     for (const auto& material : g_meshMaterialInstances) {
         engine->destroy(material.second);
     }
@@ -203,8 +205,6 @@ static void cleanup(Engine* engine, View*, Scene*) {
         engine->destroy(i);
     }
 
-    g_meshSet.reset(nullptr);
-
     engine->destroy(g_params.light);
     engine->destroy(g_params.spotLight);
     engine->destroy(g_colorGrading);