Fixed bug when dealing with empty input, also improved error messages for unknown ANSI prefix

grep-mtime-sorter.mjs

@@ -10,6 +10,7 @@ and has only been superficially tested. It should be considered experimental and
 
 import fs from 'node:fs';
 import { stat } from 'node:fs/promises';
+import { inspect } from 'node:util';
 
 const lineRe = /^\x1b\[35m\x1b\[K(.*?)\x1b/;
 
@@ -35,7 +36,7 @@ async function getMtime(line) {
 			return 0;
 		}
 	} else {
-		throw new Error('Malformed input: ANSI prefix not found');
+		throw new Error(`Malformed input: ANSI prefix not found for line ${inspect(line)}`);
 	}
 }
 
@@ -47,7 +48,7 @@ async function main() {
 		process.stdin.on('end', () => { resolve(data); });
 	});
 
-	const lines = input.split(/(?<=\n)/);
+	const lines = input.split(/(?<=\n)/).filter(line => line.trim().length > 0);
 
 	const pairs = await Promise.all(
 		lines.map(async (line, index) => {