From 6bac067488c7d559371ab6d940b79f5e7c41f461 Mon Sep 17 00:00:00 2001
From: Thomas Krijnen <t.krijnen@gmail.com>
Date: Wed, 6 Feb 2019 13:33:38 +0100
Subject: [PATCH] Keep behaviour of returned null pointers for now

---
 src/ifcparse/IfcParse.cpp | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/ifcparse/IfcParse.cpp b/src/ifcparse/IfcParse.cpp
index 9e2b3bb41d..0e63c88360 100644
--- a/src/ifcparse/IfcParse.cpp
+++ b/src/ifcparse/IfcParse.cpp
@@ -1807,11 +1807,13 @@ IfcEntityList::ptr IfcFile::entitiesByReference(int t) {
             ret = cached_it->second;
         }
         else {
-            ret.reset(new IfcEntityList);
-            ret->reserve((unsigned)it->second.size());
-            const std::vector<unsigned>& ids = it->second;
-            for (std::vector<unsigned>::const_iterator jt = ids.begin(); jt != ids.end(); ++jt) {
-                ret->push(entityById(*jt));
+            if (it->second.size()) {
+                ret.reset(new IfcEntityList);            
+                ret->reserve((unsigned)it->second.size());
+                const std::vector<unsigned>& ids = it->second;
+                for (std::vector<unsigned>::const_iterator jt = ids.begin(); jt != ids.end(); ++jt) {
+                    ret->push(entityById(*jt));
+                }
             }
             by_ref_cached_[t] = ret;
         }