lassie snuffle: fix "has no attribute 'detections'" bug

src/snuffling.py

@@ -70,6 +70,7 @@ class LassieSnuffling(Snuffling):
     def __init__(self):
         Snuffling.__init__(self)
         self.config = None
+        self.detections = []
 
     def setup(self):
         if self.config: