now working on linux with mariadb

rowers/interactiveplots.py

@@ -1121,6 +1121,9 @@ def fitnessmetric_chart(fitnessmetrics,user,workoutmode='rower',startdate=None,
     except TypeError:
         df = pd.DataFrame()
 
+    if df.empty:
+        return ["","no data"]
+
     groups = df.groupby(by='date').max()
 
     power4min = groups['power4min']