fix: v3bwfile: Avoid statistics without data

If mean or median argument is empty, they throw an exception.
This can happen when the scanner has stopped and the result is
stored as successful without any downloads.

Closes: #40012

sbws/lib/scaling.py

@@ -14,6 +14,10 @@ def bw_filt(bw_measurements):
     It is the equivalent to Torflow's ``filt_sbw``.
     ``mu`` in this function is the equivalent to Torflow's ``sbw``.
     """
+    mu = 1
+    if bw_measurements:
         mu = mean(bw_measurements)
-    bws_gte_mean = filter(lambda bw: bw >= mu, bw_measurements)
+    bws_gte_mean = list(filter(lambda bw: bw >= mu, bw_measurements))
+    if bws_gte_mean:
         return mean(bws_gte_mean)
+    return 1

sbws/lib/v3bwfile.py

@@ -869,13 +869,19 @@ class V3BWLine(object):
 
     @staticmethod
     def bw_median_from_results(results):
-        return max(round(median([dl['amount'] / dl['duration']
-                                 for r in results for dl in r.downloads])), 1)
+        bws = [dl['amount'] / dl['duration']
+               for r in results for dl in r.downloads]
+        if bws:
+            return max(round(median(bws)), 1)
+        return 1
 
     @staticmethod
     def bw_mean_from_results(results):
-        return max(round(mean([dl['amount'] / dl['duration']
-                               for r in results for dl in r.downloads])), 1)
+        bws = [dl['amount'] / dl['duration']
+               for r in results for dl in r.downloads]
+        if bws:
+            return max(round(mean(bws)), 1)
+        return 1
 
     @staticmethod
     def last_time_from_results(results):