Fix loop-value-1-1 parsing

[TPGamesNL]

Description

The 'return null' here caused the parser to stop after the first match, even if the expression parsing failed.
For example, matching loop-value-1-1 against %number%-%number% has the first match of (loop-value)-(1-1), because that matches the pattern. However, if parsing the expression loop-value does not work, the parser is supposed to attempt (loop-value-1)-(1), because that also matches the pattern. Because of the return statement here, it doesn't do this.

The main problem with this change, is that it increases parsing time by about 17% from my tests.

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Target Minecraft Versions: any
Requirements: none
Related Issues: #2382

[APickledWalrus]

The increased parsing time is certainly not ideal, but perhaps unavoidable. Is this for every script that parsing time increases? Or ones that make use of specific syntax?

However, it is also worth nothing that there are other PRs open that will reduce parsing time as well.

That said, this gets approval anyways ;D

[TPGamesNL]

The time increase would probably be for every script.

We should consider whether it's worth to fix this bug (there's always a workaround available using brackets) for a 17% increase in parsing time.