Bug 1954181

Description of problem:
On startup, clipboard contents can be pasted to Octave GUI with Ctrl-V shortcut. This stops working after editor's context menu has been opened with right mouse click, or menu from the menu bar has been opened. This happens even if the menu is closed without selecting any option, by clicking somewhere outside the menu.

Additionally, on first menu open the Paste option is selectable but does not do anything, but on subsequent menu opens it is greyed out. 

Happens only if the clipboard is populated from another source than Octave. Copying and pasting from Octave gui back to itself works as it should.

Happens only in a Wayland session, XOrg is unaffected.

Upstream bug report: https://savannah.gnu.org/bugs/index.php?60356

Version-Release number of selected component (if applicable):
5.2.0-12.fc34

How reproducible:
Always

Steps to Reproduce:
1. Copy some text to clipboard
2. Start Octave Gui
3. Paste the text with Ctrl-V, observe success
4. Open context menu, select Paste, observe nothing happens
5. Open context menu again, observe Paste is greyed out
6. Close context menu
7. Try pasting with Ctrl-V, observe nothing happens 

Actual results:
Pasting works neither with Ctrl-V nor context menu entry.

Expected results:
Pasting works as expected.

Additional info:
Since this only affects Wayland, workaround is to force Qt to X mode:

     $ QT_QPA_PLATFORM=xcb /usr/bin/octave --gui

Perhaps this could even the fix for Fedora, at least until a proper fix is available upstream, since it seems that Octave is not completely ready for Wayland yet.