Address clippy issue regarding flatten usage

[puhley]

Changes in this pull request

This is to address the following clippy error:

note: this expression returning a `std::io::Lines` may produce an infinite number of `Err` in case of a read error
   --> src/main.rs:503:27
    |
503 |         for mal_string in lines.flatten() {
    |                           ^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lines_filter_map_ok

Checklist

• [X] This PR represents a single feature, fix, or change.
• [X] All applicable changes have been documented.
• [X] Any TO DO items (or similar) have been entered as GitHub issues and the link to that issue has been included in a comment.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 68.52%. Comparing base (c310429) to head (1901fb2).

Files	Patch %	Lines
src/main.rs	0.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #139 +/- ## ======================================= Coverage 68.52% 68.52% ======================================= Files 2 2 Lines 502 502 ======================================= Hits 344 344 Misses 158 158 ```

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