minor bugs in shift and skills plugins corrected

dream/plugins/ReadShiftFromSpreadsheet.py

@@ -31,6 +31,7 @@ class ReadShiftFromSpreadsheet(plugin.InputPreparationPlugin):
           shift_by_station.setdefault(station, []).append(
             (start_time, stop_time) )
 
+    if data['input']['operator_shift_spreadsheet']:
       for line in data['input']['operator_shift_spreadsheet'][1:]:
         if line[1]:
           # Get the dates, and convert them to simulation clock time units.

dream/plugins/ReadSkilledOperators.py

@@ -17,6 +17,7 @@ class ReadSkilledOperators(plugin.InputPreparationPlugin):
     """
     PBData=data['input'].get('operator_skill_spreadsheet', None)
     node=data['graph']['node']
+    operatorPresent = False
     if PBData:
         PBData.pop(0)  # pop the column names
         for PBitem in PBData:
@@ -32,10 +33,12 @@ class ReadSkilledOperators(plugin.InputPreparationPlugin):
               "skills":skills,
               "ouputSchedule" : 1
             }
+            operatorPresent = True
             # for every station that has one or more skilled operators set operation type to MT-Load-Processing
             for stationId in skills:
                 node[stationId]["operationType"]="MT-Load-Processing"
         # add EventGenerator for the allocation every 10 minutes
+        if operatorPresent:
           node['EV123454321']={   #(random id)
                       "name": "Allocator", 
                       "argumentDict": "{}",