Better fix for QgsVectorFileWriter segfault and test

- Revert test to 735c255 commit, excepting 'assert myResult==QgsVectorFileWriter.NoError' edit

Author: dakcarto

src/core/qgsvectorfilewriter.cpp

@@ -647,7 +647,10 @@ QgsVectorFileWriter::writeAsVectorFormat( QgsVectorLayer* layer,
   QgsVectorFileWriter* writer =
     new QgsVectorFileWriter( fileName, fileEncoding, skipAttributeCreation ? QgsFieldMap() : layer->pendingFields(), layer->wkbType(), outputCRS, driverName, datasourceOptions, layerOptions, newFilename );
 
-  QgsDebugMsg( "newFilename = " + *newFilename );
+  if ( newFilename )
+  {
+    QgsDebugMsg( "newFilename = " + *newFilename );
+  }
 
   // check whether file creation was successful
   WriterError err = writer->hasError();

tests/src/python/test_qgsvectorfilewriter.py

@@ -67,7 +67,6 @@ def testWrite(self):
         myLayerOptions = QStringList()
         mySelectedOnlyFlag = False
         mySkipAttributesFlag = False
-        myNewFileName = QString()
         myGeoCrs = QgsCoordinateReferenceSystem()
         myGeoCrs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
         myResult = QgsVectorFileWriter.writeAsVectorFormat(
@@ -80,8 +79,7 @@ def testWrite(self):
             myErrorMessage,
             myOptions,
             myLayerOptions,
-            mySkipAttributesFlag,
-            myNewFileName)
+            mySkipAttributesFlag)
         assert myResult==QgsVectorFileWriter.NoError
 
 if __name__ == '__main__':