Fix decoding empty array of complex type in RPM

src/bacnet/basic/service/h_rpm_a.c

@@ -118,6 +118,14 @@ int rpm_ack_decode_service_request(
                    more than one element to decode */
                 value = calloc(1, sizeof(BACNET_APPLICATION_DATA_VALUE));
                 rpm_property->value = value;
+
+                /* Special case for an empty array - we decode it as null */
+                if (apdu_len && decode_is_closing_tag_number(apdu, 4)) {
+                    /* NULL value has tag 0, that was already set by calloc */
+                    decoded_len++;
+                    apdu_len--;
+                    apdu++;
+                } else {
                     while (value && (apdu_len > 0)) {
                         len = bacapp_decode_known_property(apdu, (unsigned)apdu_len,
                             value, rpm_object->object_type,
@@ -154,6 +162,7 @@ int rpm_ack_decode_service_request(
                             break;
                         }
                     }
+                }
             } else if (apdu_len && decode_is_opening_tag_number(apdu, 5)) {
                 /* propertyAccessError */
                 decoded_len++;