Mask parser doesn't offer suggestions after the first block

### WorldEdit Version

7.3.4

### Platform Version

Spigot-1.21

### Confirmations

- [X] I am using the most recent Minecraft release.
- [X] I am using a version of WorldEdit compatible with my Minecraft version.
- [X] I am using the latest or recommended version of my platform software.
- [X] I am NOT using a hybrid server, e.g. a server that combines Bukkit and Forge. Examples include Arclight, Mohist, and Cardboard.
- [X] I am NOT using a fork of WorldEdit, such as FastAsyncWorldEdit (FAWE) or AsyncWorldEdit (AWE)

### Bug Description

When using -m argument in commands, I can only TAB auto-complete the first block but not the next ones.

Example: //stack 1 u -am stone,bricks,dirt
Result: when typing stone, I am shown TAB auto-complete suggestions. bricks and dirt have to be typed out manually.

### Expected Behavior

Expected behaviour:

Example: //stack 1 u -am stone,bricks,dirt
Result: when typing stone, bricks and dirt I am shown TAB auto-complete suggestions.

### Reproduction Steps

1. Have multiple blocks in a selection
2. Type //stack 1 u -am

### Anything Else?

Unless I am doing something wrong, this is a minor bug/feature that gets annoying when typing out multiple long blocks.