misc: fix missing-parentheses-for-call-in-test pylint error (#56288)

combo/apps/dataviz/models.py

@@ -434,7 +434,7 @@ class ChartNgCell(CellBase):
         chart.compute_sum = bool(response.get('measure') == 'integer' and chart.axis_count > 0)
 
         formatter = self.get_value_formatter(response.get('unit'), response.get('measure'))
-        if formatter:
+        if formatter is not None:
             chart.config.value_formatter = formatter
 
         return x_labels, y_labels, data