Fix final nits from noticeindex change.

Test: m droid dist cts alllicensemetadata
Change-Id: Ie446e5693a09f4ae1c936cdae6f1e668105541f0
diff --git a/tools/compliance/projectmetadata/projectmetadata.go b/tools/compliance/projectmetadata/projectmetadata.go
index f9ddbae..f0ad7b5 100644
--- a/tools/compliance/projectmetadata/projectmetadata.go
+++ b/tools/compliance/projectmetadata/projectmetadata.go
@@ -233,7 +233,7 @@
 
 // AllMetadataFiles returns the sorted list of all METADATA files read thus far.
 func (ix *Index) AllMetadataFiles() []string {
-	files := []string(nil)
+	var files []string
 	ix.projects.Range(func(key, value any) bool {
 		pi := value.(*projectIndex)
 		if pi.path != "" {