Alter Workflow::Instance and Cron to return empty hashrefs instead

of undef.
Fix JSON handling in Commerce::Transaction->shippingOptions.  This probably isn't a problem
now since it is never called as an accessor.

lib/WebGUI/Workflow/Cron.pm

@@ -121,7 +121,7 @@ sub get {
             return $parameters->{parameters};
         }
         else {
-            return undef;
+            return {};
         }
     }
     return $self->{_data}{$name};

lib/WebGUI/Workflow/Instance.pm

@@ -152,7 +152,7 @@ sub get {
             return $parameters->{parameters};
         }
         else {
-            return undef;
+            return {};
         }
     }
     return $self->{_data}{$name};