From f7ccf8d8438306e3d7691f856c565b7970e6391e Mon Sep 17 00:00:00 2001
From: Lonami Exo <totufals@hotmail.com>
Date: Mon, 24 Jan 2022 11:05:27 +0100
Subject: [PATCH] Fix reset_deadline check in messagebox

---
 telethon/_updates/messagebox.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/telethon/_updates/messagebox.py b/telethon/_updates/messagebox.py
index 54c23a49..1562cd21 100644
--- a/telethon/_updates/messagebox.py
+++ b/telethon/_updates/messagebox.py
@@ -220,7 +220,7 @@ class MessageBox:
         if self.next_deadline == entry:
             # If the updated deadline was the closest one, recalculate the new minimum.
             self.next_deadline = min(self.map.items(), key=lambda entry_state: entry_state[1].deadline)[0]
-        elif deadline < self.map.get(self.next_deadline, 0):
+        elif self.next_deadline in self.map and deadline < self.map[self.next_deadline].deadline:
             # If the updated deadline is smaller than the next deadline, change the next deadline to be the new one.
             self.next_deadline = entry
         # else an unrelated deadline was updated, so the closest one remains unchanged.