System: Prevent save states while memory cards are being saved

src/core/hotkeys.cpp

@@ -110,8 +110,8 @@ static void HotkeySaveStateSlot(bool global, s32 slot)
   Error error;
   if (!System::SaveState(path.c_str(), &error, g_settings.create_save_state_backups))
   {
-    Host::AddKeyedOSDMessage(
-      "SaveState",
+    Host::AddIconOSDMessage(
+      "SaveState", ICON_FA_EXCLAMATION_TRIANGLE,
       fmt::format(TRANSLATE_FS("OSDMessage", "Failed to save state to slot {0}:\n{1}"), slot, error.GetDescription()),
       Host::OSD_ERROR_DURATION);
   }

src/core/imgui_overlays.cpp

@@ -1143,7 +1143,7 @@ void SaveStateSelectorUI::SaveCurrentSlot()
     Error error;
     if (!System::SaveState(path.c_str(), &error, g_settings.create_save_state_backups))
     {
-      Host::AddKeyedOSDMessage("SaveState",
+      Host::AddIconOSDMessage("SaveState", ICON_FA_EXCLAMATION_TRIANGLE,
                                fmt::format(TRANSLATE_FS("OSDMessage", "Failed to save state to slot {0}:\n{1}"),
                                            GetCurrentSlot(), error.GetDescription()),
                                Host::OSD_ERROR_DURATION);

src/core/system.cpp

@@ -1345,6 +1345,12 @@ bool System::LoadState(const char* filename, Error* error)
 
 bool System::SaveState(const char* filename, Error* error, bool backup_existing_save)
 {
+  if (IsSavingMemoryCards())
+  {
+    Error::SetStringView(error, TRANSLATE_SV("System", "Cannot save state while memory card is being saved."));
+    return false;
+  }
+
   if (backup_existing_save && FileSystem::FileExists(filename))
   {
     Error backup_error;
@@ -1365,7 +1371,7 @@ bool System::SaveState(const char* filename, Error* error, bool backup_existing_
                          error);
   if (!stream)
   {
-    Error::AddPrefixFmt(error, "Failed to save state to '{}': ", Path::GetFileName(filename));
+    Error::AddPrefixFmt(error, "Cannot open '{}': ", Path::GetFileName(filename));
     return false;
   }