From cfc1ddee5e00ce78a59e00e604f0ce50f72f5213 Mon Sep 17 00:00:00 2001
From: Thomas Krijnen <t.krijnen@gmail.com>
Date: Sat, 4 Sep 2021 14:27:46 +0200
Subject: [PATCH] #1676 null handling in inverses

---
 src/ifcparse/IfcParse.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/ifcparse/IfcParse.cpp b/src/ifcparse/IfcParse.cpp
index 66ee47e5e4..8d1b036573 100644
--- a/src/ifcparse/IfcParse.cpp
+++ b/src/ifcparse/IfcParse.cpp
@@ -2211,7 +2211,9 @@ IfcEntityList::ptr IfcFile::getInverse(int instance_id, const IfcParse::declarat
 		if (valid && attribute_index >= 0) {
             try {
                 Argument* arg = (*it)->data().getArgument(attribute_index);
-                if (arg->type() == IfcUtil::Argument_ENTITY_INSTANCE) {
+				if (arg->isNull()) {
+					valid = false;
+				} else if (arg->type() == IfcUtil::Argument_ENTITY_INSTANCE) {
                     valid = instance == *arg;
                 } else if (arg->type() == IfcUtil::Argument_AGGREGATE_OF_ENTITY_INSTANCE) {
                     IfcEntityList::ptr li = *arg;