check ready before updating pd (#391)

- For set_nSigma only call update_pedestal if we have accumulated enough
samples otherwise just write it
- For update threshold check if pd is ready and if not throw

closes #390

python/src/bind_ClusterFinder.hpp

@@ -55,6 +55,10 @@ void define_ClusterFinder(py::module &m, const std::string &typestr) {
              &ClusterFinder<ClusterType, uint16_t, pd_type>::clear_pedestal)
         .def("update_threshold",
              &ClusterFinder<ClusterType, uint16_t, pd_type>::update_threshold)
+        .def_property_readonly(
+            "pedestal_ready",
+            &ClusterFinder<ClusterType, uint16_t, pd_type>::pedestal_ready,
+            R"(True once enough pedestal frames have been pushed to find clusters.)")
         .def_property_readonly(
             "pedestal",
             [](ClusterFinder<ClusterType, uint16_t, pd_type> &self) {