make sure we always get numeric values

organize/work/README.txt

@@ -236,7 +236,7 @@ The user interface is a ReportConceptView subclass that is directly associated w
     {'actions': [...]}
 
   >>> results.totals.data
-  {'effort': 900}
+  {'effort': 900.0}
 
 Export of work data
 -------------------

organize/work/report.py

@@ -75,6 +75,7 @@ class DurationField(Field):
 
     def getValue(self, row):
         value = self.getRawValue(row) or 0
+        value = float(value)
         if value and 'totals' in self.executionSteps:
             data = row.parent.totals.data
             data[self.name] = data.get(self.name, 0) + value