Pressing ISO_Level5_Shift inserts null character

When using a keyboard layout that has ISO_Level5_Shift modifier for inserting characters more conveniently, every ISO_Level5_Shift press gets processed as a Null character. E.g. in insert mode, holding ISO_Level5_Shift results in inserting a Null character, which is displayed like a triangle.

Using the modifier in normal mode also leads to incorrect behavior. For example, if the ')' character is produced by pressing LVL5+j, then you would expect `vi)` to select all in parentheses, but this doesn't happen as the characters get interpreted as 'v', 'i', 'null character', ')'.

It's interesting that you can map null character to <Nop> by executing this:

:imap ^@ <Nop>

, where ^@ is what you get when you press ISO_Level5_Shift in console mode. But adding this command to vimrc seems to have no effect.

I also tried to add this to vimrc:

map  <Nul> <Nop>
imap <Nul> <Nop>

Also doesn't work.

STEPS TO REPRODUCE

1. Switch to 3l keyboard layout
2. In Qt Creator FakeVim, press Cur/Num modifier in insert mode