Description of problem:
`nano --restricted` is crashing if you press the insert key on the keyboard.

Version-Release number of selected component (if applicable):
$ rpm -q nano
nano-2.9.4-1.fc28.x86_64

How reproducible:
easy, 100%

Steps to Reproduce:
1. in terminal execute:
$ nano --restricted
2. press insert key on keyboard

Actual results:
at the bottom of nano you can see
    [ This function is disabled in restricted mode ]Segmentation fault (core dumped)
(followed by the menu "^G Get Help ..." and your prompt)

Expected results:
nano should not crash

Additional info:
an unusable stack trace is: https://retrace.fedoraproject.org/faf/reports/bthash/3a8c2fdaee5138975892c9e1a4065fea1712cfb9/

With nano-2.9.4-1.fc28.x86_64 `nano` is not crashing when the insert key is pressed.

With nano-2.9.3-3.fc28.x86_64 `nano --restricted` did not crash when the insert key was pressed.