Fix negative timestamp issue

Some timestamps can be negative, and anything lower than -43200 throws OSError. Handle that by changing the `value == 0` check to `value <= 0`

telethon/extensions/binaryreader.py

@@ -120,7 +120,7 @@ class BinaryReader:
            into a Python datetime object.
         """
         value = self.read_int()
-        if value == 0:
+        if value <= 0:
             return None
         else:
             return datetime.fromtimestamp(value, tz=timezone.utc)