String literal matching throws an exception for length < 2

[bluelhf]

Describe the bug
When StringLiteral matches some input, it does not do bounds checks prior to calling String#substring(int, int) to get the potential content of the string literal. For obvious reasons, this fails for inputs of length 1 — the result is an attempted substring from index 1 inclusive to index 0 exclusive.

To Reproduce
Steps to reproduce the behavior:

1. Load this script:

on script load:
  trigger:
    // This is initially parsed as a less-than comparison,
    // causing the parser to attempt to match ", which breaks
    // string literal's content matching
    set {foo} to "Hello " + "<there!"

2. Notice the ScriptCompileError: An unknown error occurred while compiling, caused by a SIOOBE when matching " in StringLiteral.
3. Realise that you cannot set {foo} to "Hello <there!", and become overwhelmed with panic.
   Expected behavior
   The input should compile as the addition of the string literals "test" and "<hello".

Additional context
I'm running ByteSkript version 1.0.21.

Suggested changes
Add a guard condition to the matcher, which returns null if the length of the string is less than 2.

[Moderocky]

Fixed in .22