[giri256]

Fixes #585.

Empty target entries are now removed after paths are collected from direct arguments, --files-from, or --files0-from. The filter checks only for zero-length strings, so non-empty paths containing whitespace are preserved unchanged.

Added regressions for:

• blank lines in newline-delimited stdin input;
• explicit empty path arguments between valid paths.

Validation:

• cargo test
• cargo fmt --check
• git diff --check

cargo clippy --all-targets -- -D warnings remains blocked by pre-existing warnings in untouched files (tests/test_exact_output.rs, the existing header in tests/test_flags.rs, and src/config.rs).