fixing escape()

fixing escape() as replacing a None would throw an exception 'NoneType' object has no attribute 'replace'. useful in case of escaping a None string given from message.from_user.last_name as you dont know wether the user has a last name or not

telebot/util.py

@@ -399,8 +399,12 @@ def escape(text: str) -> str:
     :return: the escaped text
     """
     chars = {"&": "&amp;", "<": "&lt;", ">": "&gt;"}
-    for old, new in chars.items(): text = text.replace(old, new)
-    return text
+    if text == None:
+        return None
+    else:
+        for old, new in chars.items(): 
+            text = text.replace(old, new)
+        return text
 
 
 def user_link(user: types.User, include_id: bool=False) -> str: