Handle the case where no hitlets are fully contained in peaklets (#1529)

* Handle the case where no hitlets are fully contained in peaklets

* Set default values first

straxen/plugins/peaklets/peaklets.py

@@ -416,8 +416,14 @@ def create_outside_peaks_region(peaklets, start, end):
     @staticmethod
     def add_hit_features(hitlets, peaklets):
         """Create hits timing features."""
+        peaklets["max_diff"] = -1
+        peaklets["min_diff"] = -1
+        peaklets["first_channel"] = DIGITAL_SUM_WAVEFORM_CHANNEL
+        peaklets["last_channel"] = DIGITAL_SUM_WAVEFORM_CHANNEL
         split_hits = strax.split_by_containment(hitlets, peaklets)
         for peaklet, _hitlets in zip(peaklets, split_hits):
+            if len(_hitlets) == 0:
+                continue
             argsort = strax.stable_argsort(_hitlets["max_time"])
             sorted_hitlets = _hitlets[argsort]
             time_diff = np.diff(sorted_hitlets["max_time"])