update dear imgui from 1.92.2b-docking to 1.92.6-docking

libs/imgui/backends/imgui_impl_sdlrenderer3.cpp

@@ -26,6 +26,7 @@
 // - Introduction, links and more at the top of imgui.cpp
 
 // CHANGELOG
+//  2025-09-18: Call platform_io.ClearRendererHandlers() on shutdown.
 //  2025-06-11: Added support for ImGuiBackendFlags_RendererHasTextures, for dynamic font atlas. Removed ImGui_ImplSDLRenderer3_CreateFontsTexture() and ImGui_ImplSDLRenderer3_DestroyFontsTexture().
 //  2025-01-18: Use endian-dependent RGBA32 texture format, to match SDL_Color.
 //  2024-10-09: Expose selected render state in ImGui_ImplSDLRenderer3_RenderState, which you can access in 'void* platform_io.Renderer_RenderState' during draw callbacks.
@@ -94,12 +95,14 @@ void ImGui_ImplSDLRenderer3_Shutdown()
     ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
     IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
     ImGuiIO& io = ImGui::GetIO();
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
 
     ImGui_ImplSDLRenderer3_DestroyDeviceObjects();
 
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
     io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasTextures);
+    platform_io.ClearRendererHandlers();
     IM_DELETE(bd);
 }
 
@@ -282,10 +285,8 @@ void ImGui_ImplSDLRenderer3_UpdateTexture(ImTextureData* tex)
     }
     else if (tex->Status == ImTextureStatus_WantDestroy)
     {
-        SDL_Texture* sdl_texture = (SDL_Texture*)(intptr_t)tex->TexID;
-        if (sdl_texture == nullptr)
-            return;
-        SDL_DestroyTexture(sdl_texture);
+        if (SDL_Texture* sdl_texture = (SDL_Texture*)(intptr_t)tex->TexID)
+            SDL_DestroyTexture(sdl_texture);
 
         // Clear identifiers and mark as destroyed (in order to allow e.g. calling InvalidateDeviceObjects while running)
         tex->SetTexID(ImTextureID_Invalid);