sweep: DIRACGrid#6694 fix accounting JobsPerPilot plot

Author: aldbr

src/DIRAC/AccountingSystem/private/Plotters/PilotPlotter.py

@@ -186,8 +186,9 @@ def _plotJobsPerPilot(self, reportRequest, plotInfo, filename):
             "endtime": reportRequest["endTime"],
             "span": plotInfo["granularity"],
             "ylabel": "jobs/pilot",
-            "normalization": max(x for y in plotInfo["data"].values() for x in y.values()),
         }
+        if plotInfo["data"]:
+            metadata["normalization"] = max(x for y in plotInfo["data"].values() for x in y.values())
         return self._generateQualityPlot(filename, plotInfo["data"], metadata)
 
     def _reportTotalNumberOfPilots(self, reportRequest):