Only print out debug message if bridged channel is not NULL. (issue #8412 reported by jubilex)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.2@48157 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_iax2.c

@@ -7110,7 +7110,7 @@ retryowner:
 					if (!strcmp(ies.called_number, ast_parking_ext())) {
 						if (iax_park(ast_bridged_channel(iaxs[fr->callno]->owner), iaxs[fr->callno]->owner)) {
 							ast_log(LOG_WARNING, "Failed to park call on '%s'\n", ast_bridged_channel(iaxs[fr->callno]->owner)->name);
-						} else
+						} else if (ast_bridged_channel(iaxs[fr->callno]->owner))
 							ast_log(LOG_DEBUG, "Parked call on '%s'\n", ast_bridged_channel(iaxs[fr->callno]->owner)->name);
 					} else {
 						if (ast_async_goto(ast_bridged_channel(iaxs[fr->callno]->owner), iaxs[fr->callno]->context, ies.called_number, 1))