SDL: Move imgui render to display

Fixes crash on renderer switch.

src/duckstation-sdl/d3d11_host_display.cpp

@@ -364,6 +364,7 @@ void D3D11HostDisplay::Render()
   else
     m_swap_chain->Present(BoolToUInt32(m_vsync), 0);
 
+  ImGui::NewFrame();
   ImGui_ImplSDL2_NewFrame(m_window);
   ImGui_ImplDX11_NewFrame();
 }

src/duckstation-sdl/opengl_host_display.cpp

@@ -360,6 +360,7 @@ void OpenGLHostDisplay::Render()
 
   SDL_GL_SwapWindow(m_window);
 
+  ImGui::NewFrame();
   ImGui_ImplSDL2_NewFrame(m_window);
   ImGui_ImplOpenGL3_NewFrame();
 

src/duckstation-sdl/sdl_host_interface.cpp

@@ -1290,11 +1290,8 @@ void SDLHostInterface::Run()
       if (m_system)
         m_system->GetGPU()->ResetGraphicsAPIState();
 
-      ImGui::Render();
       m_display->Render();
 
-      ImGui::NewFrame();
-
       if (m_system)
       {
         m_system->GetGPU()->RestoreGraphicsAPIState();