fix: has_lines returns empty str instead of bool

[Strengthless]

Minimal reproducible example:

def has_lines(string: str, count: int) -> bool:
    """Return True if `string` has at least `count` lines."""
    # Benchmarks show this is significantly faster than using str.count("\n") or a for loop & break.
    split = string.split("\n", count - 1)

    # Make sure the last part isn't empty, which would happen if there was a final newline.
    return split[-1] and len(split) == count

print(has_lines("test\n", 1)) # returns True correctly
print(has_lines("test\n", 3)) # returns "" instead of False

Of course, "" in an if-statement will still evaluate to False, but it's not a good practice and probably unsafe.

This PR fixes that by adding an explicit != "" check, so that booleans are returned at all times.

Unit tests for the whole file bot/utils/helpers.py have also been included, and the test coverage for that file is now at 100%.

[vivekashok1221]

Nice catch, I'm curious how you found this.

[Strengthless]

I'm curious how you found this

To be honest, I was just writing a bunch of new tests in hope to improve the coverage, but then came across a weird AssertionError that I totally did not expect 😅