fix trimp

rowers/dataprep.py

@@ -1683,9 +1683,9 @@ def workout_trimp(w, reset=False):
 
     trimp = 0
     averagehr = 0
-    if w.trimp > 0:
+    if w.trimp is not None and w.trimp > 0:
         trimp = w.trimp
-    if w.averagehr > 0:
+    if w.averagehr is not None and w.averagehr > 0:
         averagehr = w.averagehr
 
     return trimp, averagehr