Data arriving from someone else is never clean. Trailing spaces from manual entry, blank rows where sections were separated, indentation from a copy out of a document.
Make it a reflex
Trim and drop empties before looking at anything else. It costs seconds and prevents a category of problem that is genuinely difficult to diagnose later, because the cause is invisible.
What it changes downstream
Deduplication starts working properly. Counts stop including blank rows. Comparisons against other lists stop returning nothing. Every one of those failures looks like a different problem until you know the cause.
Count before and after
The difference tells you how much of what you received was padding. A file of 5,000 rows that trims to 4,100 real entries was 900 rows of nothing — worth knowing before quoting the original figure to anyone.
Try it: Trim & Remove Empty Lines on SeoWolf's Notepad.