Reserve a little more space in initial contents for sparse table

* Even if not present we serialise a bool indicating that it's not present,
  which needs to be reserved.

renderdoc/driver/d3d12/d3d12_initstate.cpp

@@ -407,6 +407,8 @@ uint64_t D3D12ResourceManager::GetSize_InitialState(ResourceId id, const D3D12In
     uint64_t ret =
         WriteSerialiser::GetChunkAlignment() + 16 + uint64_t(buf ? buf->GetDesc().Width : 0);
 
+    ret += 16;
+
     if(data.sparseTable)
       ret += 16 + data.sparseTable->GetSerialiseSize();