[bugfix] Attribute table crashes QGIS when deleting selected

Fixes https://issues.qgis.org/issues/16492

Backport from #4535

src/gui/attributetable/qgsattributetabledelegate.cpp

@@ -94,6 +94,18 @@ void QgsAttributeTableDelegate::setModelData( QWidget *editor, QAbstractItemMode
   if ( !eww )
     return;
 
+  // This fixes https://issues.qgis.org/issues/16492
+  QgsFeatureRequest request( fid );
+  request.setFlags( QgsFeatureRequest::NoGeometry );
+  request.setSubsetOfAttributes( QgsAttributeList( ) );
+  QgsFeature feature;
+  vl->getFeatures( request ).nextFeature( feature );
+  if ( ! feature.isValid( ) )
+  {
+    // Model is out of sync (again!).
+    return;
+  }
+
   newValue = eww->value();
 
   if (( oldValue != newValue && newValue.isValid() ) || oldValue.isNull() != newValue.isNull() )