fix warning

Author: sumneko

script/files.lua

@@ -70,6 +70,9 @@ local function getRealParent(path)
         return path
     end
     local res = sys.fullpath(path)
+    if not res then
+        return path
+    end
     return getRealParent(parent) / res:filename()
 end
 

script/fs-utility.lua

@@ -571,11 +571,11 @@ function m.fileList(option)
     local keyMap = {}
     local fileList = {}
     local function computeKey(path)
-        path = fsAbsolute(path, option)
-        if not path then
+        local abpath = fsAbsolute(path, option)
+        if not abpath then
             return nil
         end
-        return path:string()
+        return abpath:string()
     end
     return setmetatable({}, {
         __index = function (_, path)