"Encrypt with GPG key" checkbox is available on all file selection dialogs, including these where this option doesn't make any sense (like "Open").
Steps to Reproduce:
1. Open LibreOffice Writer
2. Select File -> Open OR File -> Export...
In file selection dialog, "Encrypt with GPG key" option is present.
Option is not present when it doesn't impact subsequent steps.
User Profile Reset: Yes
Build ID: c1d1f859b268f650143d48f294999cda0fa57350
CPU threads: 4; OS: Linux 4.13; UI render: default; VCL: kde4;
Locale: pl-PL (pl_PL.UTF-8); Calc: group
Reproducible also on Windows 10 32-bit
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/61.0.3163.100 Safari/537.36
*** This bug has been marked as a duplicate of bug 113304 ***