* fix(lib/cli): relative paths, empty slides, and tests
This fixes two issues:
1. Empty slides are now reported as error, to prevent indexing error;
2. Changing the folder path will now produce an absolute path to slides, which was not the case before and would lead to a "file does not exist error".
A few tests were also added to cover those
* fix(lib): fix from_file, remove useless field, and more
* chore(tests): remove print
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
