chan_sip: Fix memory leaks.

In change_redirecting_information variables we use ast_strlen_zero to
see if a value should be saved.  In the case where the value is not NULL
but is a zero length string we leaked.

handle_response_subscribe leaked a reference to the ccss monitor
instance.

Change-Id: Ib11444de69c3d5b2360a88ba2feb54d2c2e9f05f

channels/chan_sip.c

@@ -23168,6 +23168,8 @@ static void change_redirecting_information(struct sip_pvt *p, struct sip_request
 		redirecting->from.number.valid = 1;
 		ast_free(redirecting->from.number.str);
 		redirecting->from.number.str = redirecting_from_number;
+	} else {
+		ast_free(redirecting_from_number);
 	}
 	if (!ast_strlen_zero(redirecting_from_name)) {
 		ast_debug(3, "Got redirecting from name %s\n", redirecting_from_name);
@@ -23175,6 +23177,8 @@ static void change_redirecting_information(struct sip_pvt *p, struct sip_request
 		redirecting->from.name.valid = 1;
 		ast_free(redirecting->from.name.str);
 		redirecting->from.name.str = redirecting_from_name;
+	} else {
+		ast_free(redirecting_from_name);
 	}
 	if (!ast_strlen_zero(p->cid_tag)) {
 		ast_free(redirecting->from.tag);
@@ -23188,13 +23192,17 @@ static void change_redirecting_information(struct sip_pvt *p, struct sip_request
 		redirecting->to.number.valid = 1;
 		ast_free(redirecting->to.number.str);
 		redirecting->to.number.str = redirecting_to_number;
+	} else {
+		ast_free(redirecting_to_number);
 	}
 	if (!ast_strlen_zero(redirecting_to_name)) {
-		ast_debug(3, "Got redirecting to name %s\n", redirecting_from_number);
+		ast_debug(3, "Got redirecting to name %s\n", redirecting_to_name);
 		update_redirecting->to.name = 1;
 		redirecting->to.name.valid = 1;
 		ast_free(redirecting->to.name.str);
 		redirecting->to.name.str = redirecting_to_name;
+	} else {
+		ast_free(redirecting_to_name);
 	}
 	redirecting->reason.code = reason;
 	ast_free(redirecting->reason.str);
@@ -24223,6 +24231,7 @@ static void handle_response_subscribe(struct sip_pvt *p, int resp, const char *r
 			ast_cc_monitor_failed(monitor_instance->core_id,
 				monitor_instance->device_name,
 				"Received error response to our SUBSCRIBE");
+			ao2_ref(monitor_instance, -1);
 		}
 		return;
 	}