Fixed error.

tasksetgen.py

@@ -55,11 +55,14 @@ def lcm(a, b):
     return (a * b) / gcd(a, b)
 
 def hyperperiod(tasks):
+    try:
         periods = [task.period for task in tasks]
         hyperperiod = periods[0]
         for period in periods[1:]:
             hyperperiod = lcm(hyperperiod, period)
         return hyperperiod
+    except IndexError:
+        return 0
 
 class Timebase(Enum):
     seconds = 1