Fix AsyncSniffer Attribute Error

Fix scenario:

> >>> from scapy.all import AsyncSniffer
> >>> sniffer=AsyncSniffer(
> ...     iface="br100",
> ...     store=False,
> ...     promisc=False,
> ... )
> >>> sniffer.start()
> >>> sniffer.stop()
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "/usr/local/lib/python3.12/dist-packages/scapy/sendrecv.py", line 1404, in stop
>     if self.continue_sniff:
>        ^^^^^^^^^^^^^^^^^^^
> AttributeError: 'AsyncSniffer' object has no attribute 'continue_sniff'

Signed-off-by: Louis Scalbert <[email protected]>

Author: louis-6wind

scapy/sendrecv.py

@@ -1401,7 +1401,7 @@ def stop(self, join=True):
         """Stops AsyncSniffer if not in async mode"""
         if self.running:
             self.stop_cb()
-            if self.continue_sniff:
+            if not hasattr(self, continue_sniff) or self.continue_sniff:
                 raise Scapy_Exception(
                     "Unsupported (offline or unsupported socket)"
                 )