chore: Improve the dropdown lang usage a bit

Author: jcs090218

Assets/JCSUnity/Scripts/UI/Dropdown/JCS_DropdownLanguage.cs

@@ -71,7 +71,11 @@ private void AddListener()
         /// </summary>
         public void Refresh()
         {
-            if (mRemoveAllOptions)
+            Refresh(mRemoveAllOptions);
+        }
+        public void Refresh(bool removeAllOptions)
+        {
+            if (removeAllOptions)
                 ClearOptions();
 
             foreach (SystemLanguage option in mOptions)

Assets/JCSUnity/Scripts/Util/JCS_UIUtil.cs

@@ -15,6 +15,7 @@
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.EventSystems;
+using MyBox;
 
 #if TMP_PRO
 using TMPro;
@@ -306,6 +307,9 @@ public static void Dropdown_AddOption(JCS_DropdownObject dd, string inText)
         /// <returns> Current selected text value. </returns>
         public static string Dropdown_GetItemValue(Dropdown dd, int index)
         {
+            if (dd == null || dd.options.IsNullOrEmpty())
+                return string.Empty;
+
             return dd.options[index].text;
         }
 
@@ -418,6 +422,9 @@ public static Dropdown Dropdown_AddOption(Dropdown dd, string inText)
         /// <returns> Current selected text value. </returns>
         public static string Dropdown_GetItemValue(TMP_Dropdown dd, int index)
         {
+            if (dd == null || dd.options.IsNullOrEmpty())
+                return string.Empty;
+
             return dd.options[index].text;
         }