fix pisa bug

lib/process/calcuators/pisa.dart

@@ -49,7 +49,7 @@ class PisaCal extends Calculator<Pisa, double> {
       vti = outputVTI;
       mrVmax = outputVelocityMax;
 
-      final outputs = ref.radius.meta.outputs;
+      final outputs = ref.trace.meta.outputs;
       for (var output in outputs) {
         if (output.name == MeasureTerms.Placeholder) {
           feature.updateStringValue(output, "");