fix broken multi-threaded scan_from_walkdir

i don't fully understand *why* this was broken but... it was

src/files.rs

@@ -151,17 +151,15 @@ pub fn scan_from_walkdir(
 				// split the entries into chunks of 32, and iterate over each chunk of entries in a separate thread
 				return entries
 					.par_chunks(CHUNKS)
-					.map(|chunk| {
+					.flat_map_iter(|chunk| {
 						chunk
 							.iter() // iter over the chunk, which is a slice of DirEntry structs
-							.partition_map::<Vec<_>, Vec<_>, _, _, _>(|entry| match scan_file(entry, canonical_paths) {
+							.map(|entry| scan_file(entry, canonical_paths))
+							.collect::<Vec<_>>() // TODO: is there a way to avoid having to collect here?
+					}).partition_map(|result| match result {
 					Ok(f) => Either::Left(f),
-								Err(e) => Either::Right(e)
-							}
-						)
-					})
-				.flatten()
-				.collect()
+					Err(e) => Either::Right(e),
+				});
 			}
 		} else {
 			// should always be false when multi-threading is disabled at compile time