message: Only update backing store if it has been allocated. Closes
diff: @@ -7740,7 +7740,7 @@ bool WrappedID3D11DeviceContext::Serialise_Unmap(SerialiserType &ser, ID3D11Reso
  }
  }
  - if(IsBackgroundCapturing(m_State))
  + if(IsBackgroundCapturing(m_State) && record->DataInSerialiser)
  {
  // if there was already backing store then normally the user wrote directly into it so we
  // don't even have to update anything, except in the case where we were verifying map
  