filer.sync: fix when excluded paths is empty

weed/command/filer_sync.go

@@ -143,7 +143,7 @@ func runFilerSynchronize(cmd *Command, args []string) bool {
 				grpcDialOption,
 				filerA,
 				*syncOptions.aPath,
-				strings.Split(*syncOptions.aExcludePaths, ","),
+				util.Split(*syncOptions.aExcludePaths, ","),
 				*syncOptions.aProxyByFiler,
 				filerB,
 				*syncOptions.bPath,
@@ -179,7 +179,7 @@ func runFilerSynchronize(cmd *Command, args []string) bool {
 					grpcDialOption,
 					filerB,
 					*syncOptions.bPath,
-					strings.Split(*syncOptions.bExcludePaths, ","),
+					util.Split(*syncOptions.bExcludePaths, ","),
 					*syncOptions.bProxyByFiler,
 					filerA,
 					*syncOptions.aPath,

weed/util/fullpath.go

@@ -63,3 +63,9 @@ func Join(names ...string) string {
 func JoinPath(names ...string) FullPath {
 	return FullPath(Join(names...))
 }
+func Split(separatedValues string, sep string) []string {
+	if separatedValues == "" {
+		return nil
+	}
+	return strings.Split(separatedValues, sep)
+}