SaveData: avoid invalid DeS transaction resource pointer (#480)

Demon's Souls treats the small transaction-resource handle as a guest pointer during the fresh-save path. Return a null resource for the observed call shape to prevent the repeatable access violation at address 0x9.

Co-authored-by: RedDv <RedDv@DESKTOP-EVNB4S8>

src/SharpEmu.Libs/SaveData/SaveDataExports.cs

@@ -787,6 +787,34 @@ public static class SaveDataExports
         LibraryName = "libSceSaveData")]
     public static int SaveDataCreateTransactionResource(CpuContext ctx)
     {
+        // Demon's Souls first-run call:
+        // RDI = 0xC0000, RSI = RDX + 8, RDX = resource output.
+        // Writing integer handle 1 makes the title dereference [1 + 8],
+        // causing the repeatable access violation at guest address 0x9.
+        var desWorkSize = ctx[CpuRegister.Rdi];
+        var desWorkAddress = ctx[CpuRegister.Rsi];
+        var desResourceAddress = ctx[CpuRegister.Rdx];
+
+        if (desWorkSize == 0xC0000 &&
+            desResourceAddress != 0 &&
+            desResourceAddress <= ulong.MaxValue - sizeof(ulong) &&
+            desWorkAddress == desResourceAddress + sizeof(ulong))
+        {
+            if (!ctx.TryWriteUInt64(desResourceAddress, 0))
+            {
+                return SetReturn(
+                    ctx,
+                    (int)OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT);
+            }
+
+            TraceSaveData(
+                $"create_transaction_resource_des_guard " +
+                $"work_size=0x{desWorkSize:X} " +
+                $"work=0x{desWorkAddress:X} " +
+                $"resource_addr=0x{desResourceAddress:X} resource=0x0");
+
+            return SetReturn(ctx, 0);
+        }
         var userId = unchecked((int)ctx[CpuRegister.Rdi]);
         var reserved = ctx[CpuRegister.Rsi];