Command syntax help doesn't handle optional argument chains correctly

To reproduce

1. Type in /particle crit ~ ~ ~
2. Add a space
3. Hit esc
4. Look at the command syntax help: [<delta>] <speed> <count> [force|normal]

The displayed syntax suggests that the <delta> argument can be left out while still specifying <speed> <count> [force|normal].

Attached screenshot shows similar situation with /particle's 18w02a syntax.