Created attachment 158982 [details]
gdb backtrace

In Draw and Impress, if I select some text and click the "Text direction from top to bottom" toolbar icon, the application crashes.

Steps to Reproduce:
1. Open Impress, hit Cancel if the choose template dialog opens.
2. Type in "abc" in the "Click to add Title" area, select the typed text "abc" with your cursor.
3. Click "View > Toolbars > Text Formatting" to activate the text formatting toolbar, move the toolbar to a new row so that you can see the "Text direction from top to bottom" toolbar icon.
4. Click the "Text direction from top to bottom" icon.

--> Crash at step 4.

Gdb backtrace attached (generated from a symbols-only debug build).

Version: 7.0.0.0.alpha0+
Build ID: f0c8312bc6630ed64f174acc6f65bb5172765951
CPU threads: 4; OS: Linux 5.5; UI render: default; VCL: gtk3; 
Locale: zh-CN (zh_CN.UTF-8); UI-Language: en-US
Calc: threaded
Fedora 31 x64.

Also on the latest master, and in 6.3.5.2.

This bug was originally reported by "grassvalley" in the LibreOffice Chinese discussion forum: 
https://bbs.libreofficechina.org/forum.php?mod=viewthread&tid=2426
The reporter has reported that this bug is also reproducible in Ubutnu 19.10 X64, including the version provided by Ubuntu and also the appimage version. Also reproducible in windows10 x64.