This is to prevent NULL pointers when creating a standalone text service
that doesn't have any text set and then using functions like EM_SETSEL.
This NULL pointers doesn't happen when creating a richedit windows, because
it sets an empty text when the richedit window procedure handles the WM_CREATE event.
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v2: riched20: Set empty text by default in CreateTextServices.
https://gitlab.winehq.org/wine/wine/-/merge_requests/2941