Description:
When using LibreOffice Writer the program crashes (goes to "not responding" and has to be force closed) if I try to type a word beginning "fi" while bold and underlined. I can type those same characters if they're in the middle of a word but not if there's a space at the front.

Steps to Reproduce:
1. Make text both bold and underlined.
2. Type a new word beginning with "fi".

Actual Results:
The program freezes for a few seconds before it's shown to be nonresponsive and has to be force closed.

Expected Results:
There should be no issue normal text into the program.


Reproducible: Always


User Profile Reset: Yes



Additional Info:
Version: 6.3.5.2 (x64)
Build ID: dd0751754f11728f69b42ee2af66670068624673
CPU threads: 8; OS: Windows 10.0; UI render: default; VCL: win; 
Locale: en-GB (en_GB); UI-Language: en-US
Calc: CL