From dbd3e2c53d2fb0c19a08a0fe8780df5eb4f89476 Mon Sep 17 00:00:00 2001
From: Craig Scott <craig.scott@crascit.com>
Date: Thu, 16 Aug 2018 22:22:13 +1000
Subject: EXPORT_PROPERTIES: Prevent null dereference for undefined property

Fixes: #18260
---
 Source/cmExportFileGenerator.cxx | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Source/cmExportFileGenerator.cxx b/Source/cmExportFileGenerator.cxx
index 5f61571..9e6560f 100644
--- a/Source/cmExportFileGenerator.cxx
+++ b/Source/cmExportFileGenerator.cxx
@@ -1143,6 +1143,11 @@ bool cmExportFileGenerator::PopulateExportProperties(
         return false;
       }
       auto propertyValue = targetProperties.GetPropertyValue(prop);
+      if (propertyValue == nullptr) {
+        // Asked to export a property that isn't defined on the target. Do not
+        // consider this an error, there's just nothing to export.
+        continue;
+      }
       std::string evaluatedValue = cmGeneratorExpression::Preprocess(
         propertyValue, cmGeneratorExpression::StripAllGeneratorExpressions);
       if (evaluatedValue != propertyValue) {
-- 
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