Command syntax help text can be empty for trailing selectors in some cases

The bug

It looks like the command syntax help text can be empty in some cases and is therefore just a thin dark line is displayed above the entered command.

How to reproduce

Enter one of the following commands

# ! There is a whitespace at the end
/clear @e[] 

/clear @e[]]

When writing a fake player name, see MC-124722 and MC-124725

/team join test #fakePlayer