allow for inputdata arg to me missing. Fix #8404 (#8407)

src/python/CRABInterface/RESTUserWorkflow.py

@@ -342,7 +342,7 @@ def validate(self, apiobj, method, api, param, safe): #pylint: disable=unused-ar
             validate_str("publishname2", param, safe, RX_ANYTHING, optional=True)
 
             if safe.kwargs['jobtype'] == 'PrivateMC':
-                if param.kwargs['inputdata'] or 'inputblocks' in param.kwargs:
+                if param.kwargs.get('inputdata', None) or 'inputblocks' in param.kwargs:
                     msg = "Invalid 'inputdata' parameter."
                     msg += " Job type PrivateMC does not take any input dataset."
                     msg += " If you really intend to run over an input dataset, then you must use job type Analysis."