Update ConcaveHull.py

Correct qgis:dissolve algorithm call

Author: mdouchin

python/plugins/processing/algs/qgis/ConcaveHull.py

@@ -99,7 +99,7 @@ def processAlgorithm(self, progress):
         #dissolve all Delaunay triangles
         progress.setText(self.tr('Dissolving Delaunay triangles...'))
         dissolved = processing.runalg("qgis:dissolve", delaunay_layer,
-                                      True, '', None)['OUTPUT']
+                                      None, None)['OUTPUT']
         dissolved_layer = processing.getObject(dissolved)
         #save result
         progress.setText(self.tr('Saving data...'))