System: Fix crash with replacement precaching

src/core/imgui_overlays.cpp

@@ -127,6 +127,12 @@ static std::tuple<float, float> GetMinMax(std::span<const float> values)
 void Host::DisplayLoadingScreen(const char* message, int progress_min /*= -1*/, int progress_max /*= -1*/,
                                 int progress_value /*= -1*/)
 {
+  if (!g_gpu_device)
+  {
+    Log_InfoPrintf("%s: %d/%d", message, progress_value, progress_max);
+    return;
+  }
+
   const auto& io = ImGui::GetIO();
   const float scale = ImGuiManager::GetGlobalScale();
   const float width = (400.0f * scale);

src/core/system.cpp

@@ -1456,6 +1456,10 @@ bool System::BootSystem(SystemBootParameters parameters)
     }
   }
 
+  // Texture replacement preloading.
+  // TODO: Move this and everything else below OnSystemStarted().
+  g_texture_replacements.SetGameID(s_running_game_serial);
+
   // Good to go.
   s_state = State::Running;
   SPU::GetOutputStream()->SetPaused(false);
@@ -3355,7 +3359,8 @@ void System::UpdateRunningGame(const char* path, CDImage* image, bool booting)
     }
   }
 
-  g_texture_replacements.SetGameID(s_running_game_serial);
+  if (!booting)
+    g_texture_replacements.SetGameID(s_running_game_serial);
 
   if (booting)
     Achievements::ResetHardcoreMode();