Made ManifestPath OptionalPath instead of Path

because it is actually an optional value.

Bug: 158843648
Test: m nothing
Change-Id: If323eacf6a7aa83dcf5ce4825ad8cabeeaa97ac9
diff --git a/java/dexpreopt.go b/java/dexpreopt.go
index b4cf012..3571590 100644
--- a/java/dexpreopt.go
+++ b/java/dexpreopt.go
@@ -221,7 +221,7 @@
 		DexLocation:     dexLocation,
 		BuildPath:       android.PathForModuleOut(ctx, "dexpreopt", ctx.ModuleName()+".jar").OutputPath,
 		DexPath:         dexJarFile,
-		ManifestPath:    d.manifestFile,
+		ManifestPath:    android.OptionalPathForPath(d.manifestFile),
 		UncompressedDex: d.uncompressedDex,
 		HasApkLibraries: false,
 		PreoptFlags:     nil,