Glass cutter - Githubissues

Short Description

The glass cutter was not cutting vanilla glass

I flipped the null check

N/A

[x] I have fully tested the proposed changes and promise that they will not break everything into chaos.
[x] I have also tested the proposed changes in combination with base Slimefun and made sure nothing breaks/unexpected happens.
[x] I followed the existing code standards and didn't mess up the formatting.
[x] I did my best to add documentation to any public classes or methods I added which may not be obvious to maintainers.
[x] I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values