internal/modsdir: Fix Dropped Error (#24600)

* internal/modsdir: fix dropped error

* fix typo to unmarshalling

Co-authored-by: Daniel Dreier <danieldreier@users.noreply.github.com>

internal/modsdir/manifest.go

@@ -77,7 +77,9 @@ func ReadManifestSnapshot(r io.Reader) (Manifest, error) {
 
 	var read manifestSnapshotFile
 	err = json.Unmarshal(src, &read)
-
+	if err != nil {
+		return nil, fmt.Errorf("error unmarshalling snapshot: %v", err)
+	}
 	new := make(Manifest)
 	for _, record := range read.Records {
 		if record.VersionStr != "" {