Do not lint deleted files

[facumenzella]

Motivation

While working on something else I noticed that the pre-commit hook is broken, and tries to lint deleted files. This fixes that by checking if the file was deleted

      status=$(git status --porcelain "$file" | cut -c1-2)

It also adds another validation checking if the variables exist before using them, to prevent another error:

.git/hooks/pre-commit: line 52: [: =: unary operator expected
.git/hooks/pre-commit: line 52: [: =: unary operator expected
.git/hooks/pre-commit: line 52: [: =: unary operator expected
.git/hooks/pre-commit: line 52: [: =: unary operator expected
.git/hooks/pre-commit: line 52: [: =: unary operator expected
``

[JayShortway]

THANK YOU! 🙏