Description:
Memory taken by soffice.bin keeps increasing when a password protected .xlsx spreadsheet is opened through "File" -> "Recent Documents" list in Calc. I use openSUSE Tumbleweed with KDE Plasma 5 (X version, not Wayland). LibreOffice is from the official repository. This problem has been there for more than one month (maybe two or more).

Steps to Reproduce:
1. Create a new spreadsheet in Calc,
2. Save as .xlsx format and check "Protect with password",
3. Close the document,
4. Open the saved document through "File" --> "Recent Documents" and input the password,
5. Open KSysGuard to watch the increasing memory usage of soffice.bin

Actual Results:
Memory taken by soffice.bin keeps increasing from several hundred MB to several GB until I kill the process.

This issue also occurs within a newly created system account.

Expected Results:
The document was used to be opened almost instantly after correct password had been entered.


Reproducible: Always


User Profile Reset: Yes



Additional Info:
Version: 6.1.0.3
Build ID: 10(Build:3)
CPU threads: 4; OS: Linux 4.18; UI render: default; VCL: gtk3_kde5; 
Locale: en-GB (en_GB.UTF-8); Calc: group threaded

"Use OpenGL for all rendering" is unchecked in LibreOffice although the operation system has OpenGL enabled as follows,
```cnzhx@ostp:~> glxinfo | grep OpenGL
OpenGL vendor string: Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) HD Graphics 620 (Kaby Lake GT2)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.1.6
OpenGL core profile shading language version string: 4.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 3.0 Mesa 18.1.6
OpenGL shading language version string: 1.30
OpenGL context flags: (none)
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 18.1.6
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
OpenGL ES profile extensions:

```