bug description: after menu is displayed I get a segfault when trying to hover over the last menu
entry. it looks like under some circumstances menu->entries[] gets accessed past the last valid
value (off by one).
how to reproduce:
right-click desktop to show menu and keep right mouse button pressed
sweep mouse up-down the menu a few times - it crashes all the time between 1-5 sweeps
this commit fixes the unwanted behaviour, in active use since december 2021.
