make ImguiModule safe to unload

modules/ImguiModule/src/ImguiModule.cpp

@@ -17,6 +17,9 @@ ImguiModule::ImguiModule(Archimedes::App* a, void* h = nullptr) : Archimedes::Mo
 
 ImguiModule::~ImguiModule() {
  
+    WindowModule* wm = (WindowModule*) moduleInstances["WindowModule"];
+    wm->getRenderer()->getCmdList().erase(rcmd_it);
+    
     ImGui_ImplOpenGL3_Shutdown();
     ImGui_ImplGlfw_Shutdown();
     ImGui::DestroyContext();
@@ -61,6 +64,8 @@ void ImguiModule::onLoad() {
         ImGui::NewFrame();
     });
 
+    rcmd_it = --wm->getRenderer()->getCmdList().end()++;
+
     //Compute first frame ahead of first WindowModule->run()
     ImGui_ImplOpenGL3_NewFrame();
     ImGui_ImplGlfw_NewFrame();

modules/ImguiModule/src/ImguiModule.h

@@ -23,6 +23,8 @@ class ImguiModule : public Archimedes::Module {
     private:
         
         ImGuiContext* context;
+
+        std::list<std::function<void()>>::iterator rcmd_it;
 };
 
 #ifdef IMGUIMODULE_DYNAMIC