Add a test for rule based labeling without setting

Author: Hugo Mercier

tests/src/python/test_qgssymbollayer_createsld.py

@@ -32,7 +32,7 @@
     QgsFontMarkerSymbolLayer, QgsEllipseSymbolLayer, QgsSimpleLineSymbolLayer,
     QgsMarkerLineSymbolLayer, QgsMarkerSymbol, QgsSimpleFillSymbolLayer, QgsSVGFillSymbolLayer,
     QgsLinePatternFillSymbolLayer, QgsPointPatternFillSymbolLayer, QgsVectorLayer, QgsVectorLayerSimpleLabeling,
-    QgsTextBufferSettings, QgsPalLayerSettings, QgsTextBackgroundSettings)
+    QgsTextBufferSettings, QgsPalLayerSettings, QgsTextBackgroundSettings, QgsRuleBasedLabeling)
 from qgis.testing import start_app, unittest
 from utilities import unitTestDataPath
 
@@ -1053,6 +1053,13 @@ def testRuleBasedLabels(self):
         ltValue = gt.childNodes().item(1)
         self.assertEqual("1000000", gtValue.toElement().text())
 
+        # check that adding a rule without settings does not segfault
+        xml1 = dom.toString()
+        layer.labeling().rootRule().appendChild(QgsRuleBasedLabeling.Rule(None))
+        dom, root = self.layerToSld(layer)
+        xml2 = dom.toString()
+        self.assertEqual(xml1, xml2)
+
     def updateLinePlacementProperties(self, layer, linePlacement, distance, repeat, maxAngleInternal=25, maxAngleExternal=-25):
         settings = layer.labeling().settings()
         settings.placement = linePlacement