From 222f3ad9e01dd80cb2ff00bfedb112662594db44 Mon Sep 17 00:00:00 2001
From: Alessandro Pasotti <elpaso@itopen.it>
Date: Thu, 19 Apr 2018 19:19:31 +0200
Subject: [PATCH] Check for index validity and do not crash!

---
 src/core/qgsvectordataprovider.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/core/qgsvectordataprovider.cpp b/src/core/qgsvectordataprovider.cpp
index 0e6d3c776c6..fb863da7933 100644
--- a/src/core/qgsvectordataprovider.cpp
+++ b/src/core/qgsvectordataprovider.cpp
@@ -426,6 +426,12 @@ QVariant QgsVectorDataProvider::maximumValue( int index ) const
 
 QStringList QgsVectorDataProvider::uniqueStringsMatching( int index, const QString &substring, int limit, QgsFeedback *feedback ) const
 {
+  QStringList results;
+
+  // Safety belt
+  if ( index < 0 || index >= fields().count() )
+    return results;
+
   QgsFeature f;
   QgsAttributeList keys;
   keys.append( index );
@@ -438,7 +444,6 @@ QStringList QgsVectorDataProvider::uniqueStringsMatching( int index, const QStri
   QgsFeatureIterator fi = getFeatures( request );
 
   QSet<QString> set;
-  QStringList results;
 
   while ( fi.nextFeature( f ) )
   {