chan_iax2.c: Avoid crash with IAX2 switch support.

A change made in 82cebaa0 did not properly handle the case when a
channel was not provided, triggering a crash. ast_check_hangup(...)
does not protect against NULL pointers.

Fixes #180

diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index 5b3caf03b540d9c9c301ee23534b5843816e8ebe..3f8e5c1d328259c21592c2b3e48db0833e8085ca 100644 (file)
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -14323,7 +14323,7 @@ static struct iax2_dpcache *find_cache(struct ast_channel *chan, const char *dat
                        ast_log(LOG_WARNING, "Timeout waiting for %s exten %s\n", data, exten);
                }
 
-               if (ast_check_hangup(chan)) {
+               if (chan && ast_check_hangup(chan)) {
                        doabort = 1;
                }