canvas/preview: Account for changed QAbstractItemView.dataChanged in Qt5

Author: ales-erjavec

Orange/canvas/preview/previewbrowser.py

@@ -84,7 +84,7 @@ def updateGeometries(self):
         QListView.updateGeometries(self)
         self.updateGeometry()
 
-    def dataChanged(self, topLeft, bottomRight):
+    def dataChanged(self, topLeft, bottomRight, roles=[]):
         """Reimplemented"""
         QListView.dataChanged(self, topLeft, bottomRight)
         self.updateGeometry()